Assuming you are an overstayer who has applied for a spouse visa from the UK here is my experience, hopefully it is of some help.
---
I have spoken to solicitors who claim they can win spouse visa cases where the applicant is an overstayer but I have yet to speak to a single applicant who has been successful.
I spoke to somebody quite high up in uk immigration who said going back was the only way and that I was being badly advised by my solicitor.
On top of this my MP advised against going against the advice of the solicitor which left us completely unsure as to what to do.
We didn't know who to believe but having read up on the subject, and just wanting the visa resolved it was very clear that going back to apply was the only option that we had any control over even though we were advised by the solicitor it was a very bad idea.
We sacked the solicitor, went back, and got a visa for my wife in two days.
I am obviously very pleased we didn't apply in the UK and I think you should really consider going back to apply if it is at all possible, however I appreciate more than most what a big decision this is and that it has the potential to go disasterously wrong!
I can guarantee to you the HO will fight your appeal all the way as they have a very definate policy on this, and they seem to be getting ever more strict with those who don't want to follow their rules.
That said if you do appeal you will need a very good, experienced, OISC solicitor. We cannot advise what to do to 'cover every angle' but I would ensure you find out from your solicitor exactly what they are going to do for you and why they think they can win an appeal.
Also ensure you read the the OISC rules and understand your rights.
http://www.oisc.gov.uk/
