The £250-£350 price range is wishful thinking. TBCs were already double that price several years ago, and are now about triple on average. Your request is like me wanting to a buy a new 2020 car, but at 2005 prices.
For that low of a budget -- which will probably still be upped some -- you'd be looking at an ES10/15 combo'd with a DataVideo DVK unit. You'll get ES10/15 side effects (posterization, aggressive NR, possibly luma value offset for PAL), but it will be 99% as effective.
Note: Some of those units you list are NTSC-only, not PAL.
Some also have multiple generations, and certain gens are less PAL-friendly.
Also be aware of just buying by the model number. As example, there are both good and bad 1T-TBC units. You don't want to randomly buy the wrong item from eBay
, regardless of whether the low-video-knowledge seller claims it "work great".