There are certainly plenty of people who would wait two hours for a direct train rather than risk a connection (even if that connection is on an island platform with the traincrew making that same change of trains and offering to carry your cases for you). They are largely a captive market though, one way or another they will be getting a train. What we don't see are the ones who say "sod it, I'll drive". Quantifying those is rather difficult.But how significant a factor is it? That's the question this thread is posing. Because railheading is a symptom of the last-mile problem, so understanding the causes of these things is important to decarbonisation of our lifestyle.
You are correct though that the planning of the connection and its perceived reliability are bigger factors for many people rather than "avoid connections at all costs".
Most of the Swiss population don't live in the Alps. Most of the UK population don't live in the South East come to that. I have no doubt though that the Swiss model would work anywhere in the UK, even if very rural routes are low frequency (TPD rather than TPH) different modes should be designed to connect.The swiss do what works for them. You're not suggesting that London and the South East is an Alpine Valley, are you?
Which is what TfW's services out of Holyhead and Birmingham (imperfectly) do. They provide an hourly service to Shrewsbury before going their different ways to provide two-hourly direct services between Holyhead and Birmingham, Holyhead and Cardiff, and Aberystwyth and Birmingham.Nothing says you couldn't alternate the destinations to provide two-hourly through services if people like that.
It provides a regular service for medium distance travellers while still offering a choice of several departure times for long-distance travellers to travel direct. An effective hourly service is provided for those who don't mind the quick change at Shrewsbury (except on the Cardiff flow where until Liverpool-Cardiff is added in you'll have to wait for a train from Manchester).