For a UK licence to be valid it must have the following:
Licence document within validity period (Life, 10 yrs or 5 yrs)
Valid aircraft rating (SEP 24 months) i.e. validity date not passed.
Valid Medical (6 mths - 5 years depending on age)
All signed by licensee
If you don't meet all of these criteria your UK licence is not valid and your FAA validation Certificate is not valid either.