Wilson is actually producing putters with backweights already. And since you're in the UK wilson is pretty popular (i think) maybe you could demo one at a shop.
Otherwise you can play with back-weighting on your own. Get about 4-5 quarters to start with and tape them to the end of your grip on your putter and see how you like the feel. Keep adding quarters until you really make some SMOOOOOOTH strokes.
Its funny, my g/f is the worst putter in the world. I let her swing my putter when i was experimenting with backweighting and i couldn't believe how much improved it was. It was seriously like an F versus a C if i was grading her stroke.
I ended up with about 8-9 quarters. When i get my new putter i'm going to backweight it with a screw probably as the balance certified stuff is expensive.
I've also heard someone who made a backweight that is adjustable via up/down the shaft without removing a grip and it locks in place so its USGA conforming. Its not out yet though.
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I'm not a TGM or PGA certified Pro, but I did stay at a Holiday Inn Express last night
The feel of a backweighted putter is COMPLETELY different and the effect it has on swingweight doesn't matter imo because you can't feel the head. The weight is in your hands. Its very hard to describe. Experiment like i said with some quarters and you'll eventually see what i mean
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I'm not a TGM or PGA certified Pro, but I did stay at a Holiday Inn Express last night