Cheapest way of hour building in the UK?
 

As in the title, im after the cheapest means to build hours..

Can anyone help?

You may try and search for places like banner towing/glider towing. And work for free for them. Thats the cheapest way to build hours. But you should be able to relocate anywhere.

open your favorite aircraft sales web site, look for popular models, such as c150, c172, pa28. Notice any guys/organizations selling multiple aircraft - these guys are probably dealers. Call them up, state your case, more than likely they have a c150 sitting there with couple of hours on the clock left before needing annual/overhaul whatever else and they will be happy to rent it out for you for peanuts IF you buy something like 20 tach hours and promise to use them within a month (use them or lose them anyway).

Get Diane Abbott to fill out your log book.

Doesn'it require 50 hours as PIC on gliders in order to be able to tow gliders?
Or a CPL, but since you'd be hours building towards a CPL this would not be of any help.

Conditions vary between clubs with some requiring up to 100hr P1, I know some small clubs wouldn't mind an ad-hoc extra volunteer tug pilot but most clubs, especially the bigger ones rightly require gliding experience to at least a solo standard, if not closer to cross country standard so the pilots know what they're doing.
As such, I know for a fact that applicants have been turned down for positions due to a lack of gliding experience.

But if you're already involved or happy to get involved with flying gliders there's great opportunities available, I know one chap who got the vast majority of his hours for CPL for free and got accommodation and some food included too. Did help he started Gliding in his teens though!

Banner towing could be a possibility but I know very few operations like that.

Best of luck.

Buy a cheap LAA permit aeroplane, go touring in it, do all your own maintenance, when you've got enough hours sell it at a bargain price for the next person.