Thank you that's great Keith - actually it was our main residence from 1993 to 1997 and we must have spent over £100k renovating it - but no longer have receipt to prove so?
All change then, this alters the whole position. Only the period in which it was not your main residence is relevant. Work out your total ownership time in months, say 384 months. Work out the non occupational and deduct 18 [you are deemed to be in occupation for the last 18 months even if this is not the case]; say 336. Thus 318/384 of the gain is subject to CGT, say 83%. Not much, but better than a poke in the eye with the proverbial sharp stick; reduces your worst case to say 51.3k tax due (say 26K each).
Thank you for your support.