Sorry to be late to this thread and hope the OP returns to read this.
My end-to-end (LEJOG) was solo and unsupported in 9 days.
https://ridewithgps.com/routes/8592623
I stayed in (inexpensive) B&Bs, hostels and two nights with relatives/friends. I would budget for £30 per night (x 10) B&B.
I probably spent £20 a day on food, including evening meals (eg local pub, Wetherspoons, F&C before finishing off the day's ride).
I took ferries Padstow-Rock, Ardrossan-Brodick, Lochranza-Claonaig, Oban-Craignure, Fishnish-Lochaline, the Corran ferry (S of Ft William). Cost ~£20
And getting back:,JoG-Burwick, and Kirkwall-Aberdeen. Cost: £41 (+ £24 for 'reclining berth' on overnight ferry). See
this post.
I trained down to Penzance (effectively from London - cost £44) and got back from JoG via the Orkneys, Aberdeen and flew into Heathrow (with bike as (gratuitous) hold luggage) air fare was £56 (!). (Back at work 23 hours after finishing at JoG.)
Have a look at the thread I started a while ago (which attracted useless contributions btw):
https://www.cyclechat.net/threads/lejog-how-much-does-could-should-it-cost.197045/
In preparation, inter alia, I read a lot of riders' accounts of their rides to learn from their experience. My ride went to plan (PPPPPP) with the significant aberration being a tyre threatening to fail (detected 100 miles in to Day 4 at 680km) and needing replacement after bike shop closing hours (before a 7am start to Day 5 (224km) and then needing to ditch the rear mudguard because the new tyre (M+ 28-622) was too deep/high.