In central Scotland, (Lanark, Carluke ect, where you work) Your best bet may be the sell by installment method.
In effect, you own all the work until the rent to buy guy has paid the agreed price in full and within a certain timescale.
Get it all in writing, signed and dated by both parties. If it all goes diddies up, you still own the work, and it would be a good idea to keep the "SB" name as far as the customer is concerned until the takeover is complete in full as well.
It's hard to sell in this climate, you have to think outside the box at times.
If you find it difficult to sell, I possibly may have an interest. What is your thought's on this idea?