This includes the reduction for the survey and a deduction of £1,100.00 for premises passed.
Even with the GVS, it's too much I think. I'll have to have a think.
Did it say how many premises passed? If £700 of the discount is for the PON then I'm guessing 8 premises (£50 discount each). If you can get 1 or 2 others to join in to share the build cost, with a £500 voucher each, it might become feasible.
Sharing with one other and taking £3.5K of GBVS would leave around £2K each to pay (+VAT). With two others it would be about £1.2K each. The other parties would also have to agree to a fairly high rental of £100+VAT for the first 12 months service, but could switch after then (*).
All this is supposed to work in theory, but nobody on this forum has yet reported linking orders this way.
(*) In fact, the high first year's rental more than outweighs the £500 voucher. It would be just as well if you could informally get support from one or two others, who agree to pay a share of the install cost up front but not link orders, and they just take regular FTTP when it becomes available. They'll be able to get take FTTP service for £45+VAT per month or less, and maybe get some cashback into the deal as well. But you have to trust OpenReach to activate the properties you are expecting - linking takes the uncertainty away.