They’re just playing on time, hoping people will get bored and leave them with the money. They say they can’t issue refunds quick enough as there’s so many to do, which is probably partly true as there’s less staff to issue refunds (and you can bet the system isn’t set up to issue automatically), but even so many of these companies will be taking the mick.
Only thing you can do is issue a final letter before action, and hope that sorts it. Or be very nice to someone on the phone, if you can ever get through...