Anyone can stay in a travellers hostel . . . although it will be mainly younger folk staying.
How about after London, you get the train to Edinburgh, then stop in Glasgow on your way to Stranraer to catch the ferry to Belfast? From Belfast you can visit parts of Northern Ireland before heading South to end your trip?
Age limits in Hostels are a thing of the past. You might find some that still have age limits in Germany and Austria, but for most of Europe, it's no problem. You will find mainly young people, but I have to say that the last couple of years, also older people find their ways to hostels.
Granada is worth a visit, but it would also mean you need 2 days extra in Spain. I would say try flying, if you want to get there, as it takes quite a long trip to get there. (fly: Barcelona - Granada, and then Granada - Madrid, although the second connection is better). If you are already in Granada, then see if you are interested in Sevilla and/or Cordoba.
If you want to get to Kleve, then maybe the Airborne museum in Oosterbeek (near Arnhem) is a place to visit. It focusses on the operation Market Garden. (the failed attempt to take the bridges over the Rijn in Arnhem) http://www.airbornemuseum.org/
If I read your plans, you will need more time, to visit Europe.
enjoy your trip..when u get the chance to visit holland... maybe u can stay at the FLYING PIG HOSTEL.... My friend works there!! maybe u can check out the site...
by the way, it doesnt matter if its for youg or what... this place is for backpackers!!!!
enjoy the trip...
[ Edit: Edited on Jun 5, 2007, at 7:26 AM by omnistaffs ]