Suzydale, it's good to be prepared. The market is fairly stagnant at present and people much cleverer than you and me forecast it will fall more into line over the next couple of years, meaning you'll probably be buying when most others will be selling (this is excellent).
Without wanting to sound like your mother (or father), if I were in your shoes I'd put my partner on another management plan and set some extra financial goals between now and then. His management plan must be easy street compared to how his debts used to be?.. so he needs to be stressed a bit more before you get into bed with him (in a financial sense of course!).
When you get your first mortage you'll have a shed-load of fees to pay, say at least 1% arrangement fee, 1% legals (so say £2k at least on £100k mortgage). Most wont have the money readily available so will add it to the mortgage. Ask HIM to setup a standing order for £80 per month into YOUR account over the next 2 years ready to go towards the fees. If he can't manage that you need to fall in love with a broker (I'm not a broker and I'm too old and the wrong sex anyway)..Hope this helps..FOTW