Sorry, just to be clear: If a RMT, Osteopath, Chiropodist, Acupuncturist, Naturopath, Pedorthist, whatever asks to know exactly what your yearly coverage is (why do they even need to know?) plus wants to submit on your behalf where they get directly reimbursed, be careful. An unscrupulous location might start billing when you aren't there and max out your coverage. Are you going to complain to your insurance company that you lost all your coverage to a massage parlour? Doubt many would admit to the fraud.
On the other had, if they are just giving you receipts (safest) or submitting on your behalf but the money comes to you (still don't like them having my account details) then it isn't as bad.