Hello and welcome
I also have a Natwest loan - I asked for £678.85 in charges to be refunded - 1 prelim letter in April , 1 LBA letter in May and yesterday got an offer of the full amount from them - no mention of closing my account or anything to do with my outstanding loan with them.
Good luck - it is scary to start with - but well worth it!
Now just waiting for the cheque \0/ .... it will clear some of my huge OD!
K