Apologies for some of these late replies it was difficult to sift out some of the more personal conversations going on. It's clear one big problem with railways is simply how much they cost, and that many people can't accept that is the cost. There's another thread on why things cost so much, so that discussion can stay out there. It's also clear another issue is emotion - primarily political and heritage. This causes proponents to overlook problems and opponents to downplay benefits. Neither of these are easy things to fix.
One thing I couldn't see much discussed here is the 60-year appraisal period for whole-life costs of new schemes - I think some of these costs (such as land acquisition and a certain proportion of station and infrastructure costs) could be amortised over a much longer period, which would help give the benefits longer to repay the costs. I also think much greater weight should be given to the ongoing costs/benefits rather than lumping in the capex for every scheme.
The bus notwithstanding, even If I were travelling from Newquay to Penzance, I'd still probably get the train all the way.
This underlines the problem - you want a train, no ifs, no buts.
It's difficult to pinpoint exactly why a similar town with good rail connections will tend to do better than one without, but they seem to.
Causation and correlation are not necessarily the same thing, and economic geographies are fiendishly difficult to isolate individual causes. It'd also be interesting to see, e.g., a metric for this - GVA/capita/service option or something.
We need to look at Uckfield - Lewes again !
The reason journey time improvements weren't a significant benefit of Lewes-Uckfield is that the train simply wouldn't save that much time. Outside of a peak hour at each end of the day the A26/A27 is completely fine between Brighton and Uckfield and the majority of train journeys will be to London, which Lewes already has a faster link to. Also the 2008 study was looking at the old Hamsey link so cross-Lewes journeys were penalised by train.
BML2 is an unhelpful distraction, what should have been looked at is a route branching off at Glynde running via Ringmer (which is rapidly becoming a small town) and then rejoining the old alignment into Uckfield north of Isfield. It protects the villages (and the Lavender line) while serving Brighton-Lewes-Weald journeys, gives Falmer/Moulscoombe direct London trains, avoids the reversal and adds a long-standing dormitory town to the network. But it never even got thought of because it's not marked 'dismantled rlwy' on an old OS map and now Ringmer's filling in the most obvious gap for a station (between the Green Man pub and the Secondary School) with yet more housing.
Supporting what their constituents want is their job.
For most MPs, supporting their party seems to be their job. Although it should be pointed out that the majority of MP's constituents want lower taxes and lower train fares. So they are serving their constituents' interests by insisting on robust appraisal of public investment.
Bear in mind that frequency has consistently proven to be important for ridership...
Important yes but not the only factor. You'll note that most BCRs test a range of frequency options and in general it's a law of diminishing returns as there are only so many people who can get the trains, and once they're all on board there's nobody left to benefit but there's still a unit and crew being paid to run.