6 weeks sounds quick. Took them 8 weeks to refund me back in the summer!
I'd be interested to know if you were given a reason for that wait. Once (or if) I've heard from management in the relevant department their reasons for the time taken to process refunds, I plan to take my concerns to Passenger Focus.
In the spring I had a 6+ week wait blamed on February's storms. That was just about acceptable although that reason was only given after I'd complained. An 8 week wait in the Summer and now my 6 weeks wait in October/November says to me there are systematic problems that need addressing. It just isn't on to charge for a service and then provide a service that is nowhere near commensurate with the fee being paid.