Great thread for daydreaming while I’m at work. I would also consider youth hostels as main type of accomodation. Travelling alone they are always better because you meet folks and get chatting and that makes the whole experience better, they also serve vfm meals and drinks. May can be changeable weather, hell even August is changeable weather in the lakes so I would probably work out two loops, best possible and worst possible. The best possible take in some actual mountains. Helvellyn is good shout as it is very accessible and also has lots of routes up and down. Pooley bridge, up alongside the lake on the ‘ullswater single track’ path via cockpit and down to stay at the YHA at the base of Helvellyn would make an easy first day. Then straight up and over the mountain starting the 2nd day, then perhaps try and make it over to Watendlath to either stay at the borrowdale YHA or the indepdendent hostel Barrow House. This would put you well placed to get over to Black Sail the next day. I’ve heard it gets booked up well in advance but you might get lucky travelling alone. Get on it now! From there back to Keswick for your last day, there are buses that run over to Buttermere to and from Keswick if you can’t be bothered with the hike all the way back.
There is also a great little YHA at Buttermere as an alternative if you can’t get in at Black Sail. This is just a route straight off the top of my head so make of it what you will but does include lots of elevation. There is also buses and boats you could take advantage of if you wish to see some more of the lakes. For me I would always avoid Bowness and Ambleside, I much prefer the more remote less populated areas. There are also a number of bike hire places where you could get your 2 wheeled fix, incl Whinlatter of course, which would probably the easiest logistically. I have also had some success hitch hiking in the lakes, although this was some years ago and attitudes might be different now. Good luck and have fun, do please come back and do a thread about your trip, with pics! of course. 🙂