There are plenty of expensive bikes going for not much money on
ebay these days - search carefully and you'll pick something nice up. I've got a couple of old 'high' end/pro level 90's bikes that I've had since new, and between the two, there isn't much difference, but the posher bike is 'slightly' nicer to ride, and the DA level components are much nicer finish than the Ultegra. But, both bikes are the same geometry, run similar weight wheels and tyres, and for all purposes ride more or less the same.
I'd be wary of spending serious amounts of money on wheels. So long as they are reasonably light and spin nicely, I'm happy. I'd be worried about smashing a £2k-£4k wheelset on the state of our roads.
I like nice bikes, but the only thing that makes the difference is 'the engine'. Doesn't really matter what you ride TBH. The Tour De Manc had people on top end VR3 Colnagos, right down to folks doing the long route on hybrids. One thing I've noticed is there are a lot of folk using Gravel bikes these days - in some ways they makes a lot of sense, certainly where gear range is likely to be needed on such a hilly and long ride - I cracked out the second hand CX bike I bought last year, shoved the road tyres on, and tackled a climb that probably over half didn't get up without walking. Right tool for the job.