Thanks everyone, this has made me feel a bit better - I will still contact a solicitor though.
Sirius, do you think this is an issue or only an issue if she overstayed?
I'm not an immigration solicitor
If you want my opinion, this is one of the only two forums I have found that actually keep up to date with regualtions/realise the laws are changing and give out the correct information. I would believe what they tell you on this site. IMHO this is one of the good immigration forums and perhaps the best for partner/spouse visas?
Even some solicitors give out incorrect advice.
Don't worry, as people on here have told you, it's no big deal. Lots forget to give their change of address. I haven't seem anyone post on forums that they got refused a visa as they didn't update their address.
e.g.
Some visa holders have to report their changes to the police because of the country they are citizens of and this is a requirement on their visa. Many of those have reported they forgot to do that and then got a warning of late reporting stamped from the police. I haven't seen any of those say they have been refused a visa either.