Hi Marc, and welcome to the forum.
You will have gleaned that 2nd hand boats are a little hard to come by at the moment, I'm sure born_slippy (Roland) will be along soon to help - he's the expert at finding boats for people - in the meantime, by far your best bet to offer 29er variety would be Ronin, a fully sorted 05 rules boat, that would offer twin wire action.
I'm in Brightlingsea a lot of the time, and as you say LostHeart (Andy) is in Harwich, If you'd like to talk or have a ride contact me via the committee pages and we'll sort something out.
Graham