From what I have read of your situation so far, you are reasonably well off, not sure how you managed to get so far in debt but can understand that just a couple of bad months can cause this. From what I can see, however, I don't think you've really taken in the impact of this - you still haven't answered my question about how your boyfriend is going to inherit your bad credit and how this might impact you both?
If your situation is fairly good I would guess that the only impact is on your credit rating, and therefore you'd certainly be in a position to save before buying. However you do seem determined to get onto the housing ladder, regardless of having to pay an extra premium - which unfortunately from friends experience of lenders later - which might turn out to be a lot more difficult than you think.
I am speaking from hard experience here as myself and my partner decided to go it alone on house buying because of the impact my poor credit might have, not only on the likelihood of getting a mortgage, its size and its terms, but the fact that both of us would be basically labelled with bad credit whether the attempt succeeded or failed. Its a quite serious thing to take on. Do you really want your boyfriend to be in a position where he cannot get a normal loan or a credit card for the next 5 years and maybe more? That is something you really need to discuss.
Secondly, and again from my partner's hard learned experience, what the broker promises you and what he/she delivers might not be the same. My partner was waved a potential mortgage of 30k more than in the end they were able to get, and even then on ridiculous terms and conditions. They were not told of these ridiculous terms (i.e. parents going guarantor AND putting down a cash security of 1 years repayments for 12 months at least) initially. The broker said "you'll be in your house by the end of April" and the entire process has dragged on so much we are now wondering if we'll even have the keys by the end of June.
All I am saying is that you *could* end up very disappointed if you take this brokers advice at face value without considering the outcome and implications. You very well may end up with no mortgage, no house and your boyfriend's credit rating ruined. Think it through seriously!