I have seen considerable improvements in train speeds virtually everywere I travel by train these days, with a few excepions. Wen I first travelled from Aberdeen to Berkshire it took good 15 hours from end to end. That's via Kings Cross and Paddington. Going via the West cast was not worth thinking about. Today I travel via the west coast via Oxford, Wolverhampton and Edinburgh but return Via Aberdeen to York then from York to Oxford.
Two things make this journey fast and easier in spite of the change of trains! TRavelling aross London has always been a nightmare and anything that avoids travelling that way is a bonus. Birmingham New Street is the next to avoid wherever possible and in this case I manage not only to do both but the changes at Oxford, Wolverhampton and Edinburgh (Haymarket) are all on the same platform and it is likewise at York and Oxford on the return journey. Likewise waiting times between trains at these places are quite reasonable. So over all the journey is quite straight forwards and the trains all reasonably fast. I can't see how my journey could be made much faster and as I have mentioned, is considerably faster than the 15 hours in the latter 50's and i nto the 70's when the HST was introduced.
A lot of journies could be improved likewise with enough planning and for some realistic integration between services. As has been mentioned already it is not much fun having a fast mainline train if you have 40 minutes to two hours wait at exchange stations for the next train or bus. There is room for making these sort of changes at the moment without considering building faster lines. Sadly, with privatisation you are not going to get it as whether it is different train or bus companies they are only interested in their own patches and running them as cheaply as they can get away with.
The one change that could improved journies such. the Aberdeen services I mention would be for longer trains. In most cases the annoyance and discomfort is generally due to over crowding.
This doss tally with the thread in hand as these improvements can be made, in many cases, without increasing the speeds as at present. Going faster doesn't always mean that you are getting to your destination that much faster if the exchange times are still in an hour or more rather than in say, 15 to 20 minutes.
A good example is when I travel up to Derbyshire! With one train I get a ten-12 minute exchange at Derby but with all the others it is a 40 minute wait every time, each way. That's an hour and a half of my day waisted just at Derby, but then there is the 35-40 minutes wasted at Oxford, each way making for another hour and more wasted in my day so over all there is nearly three hours wasted in my day out just waiting at stations.
You can add these sorts of delays all over our railways.