On the HM Revenue & Customs website it says the following,
"Crown servants posted overseas
Crown servants posted overseas are treated as being in the UK provided:
they are, or were immediately prior to the posting, ordinarily resident in the UK; or
they were present in the UK immediately prior to the posting in connection with that posting. This is to ensure that people such as members of the armed forces, who may be posted abroad too quickly to enable them to establish ordinary residence in the UK before they leave, are not disadvantaged. But the person�s presence in the UK must have been in connection with the posting. It is not enough for the person just to have chosen to visit the UK before the posting began.
For tax credits, this is covered in regulations 3(2) and 5 of the Tax Credits (Residence) Regulations 2003 and for Child Benefit, this is covered in regulations 23 (2) and 30 of the Child Benefit (General) Regulations 2006."
So, assuming yir husband's in the Forces, the Tax Credits shouldn't be affected