And if you're only able to walk 2 or 3 miles a day, I wouldn't think a walking tour is viable!

I would suggest you find yourself a map of the UK (try multimap.com) to give you some idea of where you're heading, then visit some festivals- there you'll be able to join in the fringe and make contact with fellow musicians who'll give you more idea. Then the following year you'll have more contacts... etc.

Planning to attend festivals would ensure you at least enjoy your trip over while making contacts. What you are sugggesting sounds like a sure way to miss out on any fun that might be going on...

See the following threads for more info on UK festivals to visit:

UK Folk festivals
Festivals to visit in UK?
and
Festivals for newbies