I do live in St Neots, and I also commute into London by train.
Train service -
Punctuality - Mostly fine. Occasional big problems with overhead lines, points, and other big stuff, when the line is out of action for a few hours or more. More frequent niggles with cancelled trains because GNR seem to have insufficient drivers. The problem with St Neots, is that if anything big happens, then the only real solution is buses to Bedford, which takes GNR a while to sort out, and even longer to communicate with customers what is going on.
Journey - Mostly fine. The fast services in the morning are pretty full (lots more people commute in from Huntingdon), so mid week you can struggle to get a seat on the 7:18. The later trains are a little bit less busy, or alternatively you can get on the slow trains which are virtually empty at St Neots. The trains are mostly OK, but maintenance doesn't seem to be GNR's strong point, so the heating tends to be off in the winter and on in the summer.
Service - Mostly fine. A reasonable number of fast trains in the morning, but there is a big gap between the 6:37(?) and the 7:18. Half hourly fast trains from late afternoon, and an hourly fast service from 7pm until 11pm. Do not EVER catch the 19:10 in school holidays. It is the first off peak service, so is full of overtired children, and for some reason GNR use pre-war rolling stock on that service.
St Neots -
The town has changed for the better over the last five years, and is starting to emerge from the shadow of Huntingdon. Previously anything that was planned would take place in Huntingdon, the seat of the local district council. So the council is there, the police headquarters, the hospital, the cinema, etc, etc.
With the growth in population, some developments are starting to spread to St Neots, for example a cinema opened last year.
Public transport is shockingly bad in the town, and appears to be run by complete morons. For a town with many people commuting by train, there is no sensible bus service that links with the trains (the bus take 45 minutes to do a 2.5 mile journey, and is timed to miss the train by 1 minute). The last bus of the day, apart from the X5 service, is about 7pm, and there are no buses on Sundays.
Facilities - As mentioned, a cinema opened last summer, accompanied with the usual chain restaurants. That was not a bad thing, as the quality of restaurants and pubs is not great. A nice big park in the centre of town, which doubles as the flood prevention scheme when it floods in winter.
Schools, there used to be two secondary schools, a good one and a bad one. As they couldn't improve the bad one, they merged the two schools to create an average one (although the good kids still go to one campus, and the other kids still go to the other campus).
High street - Good range of supermarkets, but the high street is mainly estate agents and charity shops. Enough to survive, but you wouldn't do any serious shopping.
Surrounding towns/cities - Lots of people commute to Cambridge, and the traffic on the A428 can be horrendous in the morning and evening. And if anything happens on the A1, the town descends into gridlock. Bedford for a few better shops is not far away, Milton Keynes is 30 minutes by car. Welwyn Garden City and Peterborough up and down the train line.
The thing anyone moving out of London would notice, is how early everything shuts. It is only recently that Waitrose extended its opening hours from a 6pm closing time to 8pm. M&S Simply Food still closes at 6.30pm. Drive through town at 6pm and there is nobody around.
