Neither MSA or minimum radar altitude should be an issue. On a visual approach you should be VMC and therefor you are allowed to descend below both MSA and radar minima.
But not below any altitude restriction published in the AIP. Many UK airfields (as some have said for specific examples) have a 'do not descend below xxxx feet until established' restriction. That seems to be the best bet in this case. Name the airfield and it will be easy enough to check in the AIP
