When a Mortgage is credit Scored, the Lender will use their own scoring system and will not actually see the credit register search. Only if it fails on the search will they request a full copy.
As long as you do not have any missed payments or CCJ on the card, it will not have an adverse effect.
If you have been paying it off every month without it would not be a problem, and a balance that low is very unlikely to affect to their decision, unless your finances are extremely tight.