I have done some interesting Northern Rail end to ends, and good few European ones, over last few years, here they are:
European
Narvik-Stockholm sleeper
Narvik-Boden,
Bratislava-Split, sleeper
Berlin-Stockholm sleeper,
Hamburg-Munchen ICE overnight,
Split-Zagreb,
Frankfurt-Vienna,
Bologna-Munchen,
Warsaw-Gydynia,
Warsaw-Bielsko,
Milan-Lecce
Lecce-Florence
these were some of the better ones, but did lots of others too.
UK
Morecombe-Leeds,
Blackpool North-York,
York-Leeds via Harrogate,
Leeds-Nottingham,
Man Airport-Barrow,
Leeds-Newquay overnight HST holidaymaker train
London-Inverness day and sleeper with 37’s
London-FortWilliam sleeper with 37’s
Fishguard-Paddington HST Cardiff-Reading Non Stop,
Holyhead-Euston cab ride 47 to Chester and 86 Crewe-Euston,
Birmingham-Norwich via Ely avoiding line and 31;s-47’s
Derby-Skegness 20’s
Birmingham-Cambridge or Newmarket 31’s
these are some of the best but done many more average journeys.