I work in the financial area and certainly know that any credit check I do does not return any UK info. Unless other banks have access to UK credit bureau sites I doubt if they can get this info. However, if I was the mortgage advisor I would be asking what other committments you both have and examining past six months bank statements carefully to identify any regular payments that may be to loans. I'm not suggesting you should be dishonest but if there is nothing on your partners statements to suggest he has repayment committments it's unlikely the bank will know from credit check.