Hello to SEA222 in Canada.
There are a lot of good comments on this thread.
I'll now add mine but first our background. We had an elderly relative who lived in a flat in Lancaster about 800m south of the station where the WCML goes over the Lancaster canal and the flat was 30m-50 from the railway line which is on an embankment 20ft up. My wife is a light sleeper and she could manage a night or two but would have vetoed us buying the flat.
We have a new build home and our is Story Homes in north Cumbria - there are Story Homes on the east of Lancaster between the M6 (motorway 3 lanes each way) and a prison so these home would get 24 hour motorway noise as the M6 is busy at night with HGVs Scotland (Glasgow area) to from England. And we have some experience of the Irish Sea into which the river Lune feeds.
Canada - as you are in Canada, I would suggest you rent over here before buying and do not buy off plan.
As other have said, Persimmon do not have a good reputation - I would not buy Persimmon. We have a Story Home - the specification and design is good. The weak point - depends on the quality of the subcontractor used, some are better than others - but Story do have good after care and they do fix things.
The WCML is 24x7x365 and the freights run anytime 24 x 7. Most of the freights are long by UK standards as there are a lot of intermodals on the WCML, i.e. container flats of 25 wagons each 60ft long - so at least twice as long as a Pendolino. The track through Lancaster had a very major upgrade/replace in the last 5 years which permitted bi-directional working on all through lines 3 though platforms and 2 centre bypass/through lines and fast through lines. Pre Covid there was at least 1 fast nonstop Euston<>Glasgow each way (one was about 1600 northbound) and these go through at line speed of 90mph. The freights will go through at the freight line speed of 60 or 75 mph and will make more noise than the Pendolino and will make a racket over each point/turnout of which there is at least one on the Carlisle Bridge.
But the night maintenance will be the noisier and more at week-ends at all hours.
Think about how to get in or out of this quayside development - look at the map. Notice that Lancaster has a one way circular system round the town centre which you cannot avoid and there are only 2 ways into this quayside area - 1 past the station (Meeting House Lane) and one along the quay (St George's Quay - comes out near the bus station). The one way system is notorious for slow traffic - one of the worst times of year is November/December when the students are still at the University (which is very large) and Christmas shoppers.
Flood. It has been mentioned that the bus station flooded a few years back. Do not believe the 1 in 50 years or 1 in 100 years or 1 in 200 years predictions for flooding. Since 2000, there have been at least 3 instances of these 1 in 50/100/200s and on each occasion there was at least a months rainfall in a continuous downpour of 24-48 hours. Lancaster and Morecombe does not get the downpour. The downpours are upstream in Cumbria and the Lancaster flood was a big one where a low pressure system sat over Cumbria for 48 hours or so and it rained and rained and the rivers Derwent (Keswick/Cockermouth and out via Workington), Eden (out via Carlisle), Kent (out via Kendal) and Lune (out via Lancaster) all had floods. The river Lune heads inland east for 15 miles and then turns north up to Tebay and the Lune Gorge which is where the rain lands. Last week, June, there was 24 hours rain due to a stationary low pressure system and Seatoller (central Lake District) recorded the UK June monthly rainfall record in just the 24 hours.
The Lancaster flood took out the Holiday Inn (by the M6 J34 junction), the bus station and almost the electric power switching station that supplies all of Lancaster and Morecambe. The electric power switching station was only saved by building, very fast (in less than 24 hours) an extra flood wall 2m high around all sides and installing some pumps inside the protected area - the flood got within a few inches of overtopping the extra barrier that was added. As noted elsewhere, the bus station was up to 6 ft under water.
So you would need to walk the riverside from Skerton Bridge (A6S) past the A6N bridge (used to be the electric railway to Morecambe, and Sainsbury's (food supermarket) - this section is a raised embankment. It then becomes a raised flood wall (reinforced concrete wall) under Carlisle Bridge, past your development and on for a further 1 mile (past all the other new developments). See what you think of it and check for any gates in the wall and any drains. Ideally there should be no gates but ramps up to the top of wall level and down the other side to get from one side of the flood wall to the other. Sooner or later someone will leave a gate open or not close a gate - it has happened elsewhere and the water came in. Also any drain into the river needs to have a flap valve on the exit and the flap valve placed the correct way - Willowholme Carlisle flooded and a rumour I heard was the flap valve was installed the wrong way round and so the river was allowed in - Stagecoach Carlisle depot, the BT depot, a big Sainsbury's and McVities biscuit factory all flooded (no Ginger Nuts for months).
But the river Lune is tidal in Lancaster so the worst time is when there has been heavy rain upstream and it all comes down river at the same time as a westerly gale is blowing at a spring high tide - so westerly gale = add 1m t high tide, spring tide = add 1m to high tide and a high of water coming downstream means... This is a similar reason as to why the Thames Barrier was installed. For tide heights use Heysham Port.
And if you flood you will then have insurance problems and the next buyer will not be able to get a mortgage.