An Ensign Selfix 12-20 with Ross Xpres lens should fit the bill, try to get one where the slower shutter speeds still work properly on it. If it needs a service to restore them then it will probably cost around £50 to £70 depending on where you send it, so this model shouldn't be too expensive to service (providing nothing is broken and it's repairable!). All these folding cameras are getting on now (50 or 60+ years old), so quite a few of them need a bit of TLC to get (or keep) them fully working. The bellows usually seem to have survived quite well on the
1950s Ensign Selfixs.
If you put a bit more money to your budget then you might be able to find a good 1960s Yashica 635 TLR in fully working order for around the £80 to £100 mark, and that will give you the ability to see the focus on a viewing screen as well as 6x6 photos.
As with everything, fully research the model and look carefully at any photos and the description in any adverts, and even then, be prepared for disappointment and returning something if it's substantially not as described!
Oh, and do find a copy of the instructions and read them
thoroughly before trying to use the camera, some of them have a set order in which the shutter has to be set and primed, otherwise you can permanently damage or jam the shutter! Also, if there's a self-timer fitted then I wouldn't use it, as the mechanism is often gummed up and it can result in the shutter mechanism jamming. Best of luck finding something that suits.
