Well, I've agreed to take Trev's DGND3700v2 off him, despite it not being supported by DD-WRT and the customised firmware for DGND3700 being for v1! Regardless it should be an improvement on this sodding BT HomeHub (if it works without needing a reboot every few days that will be an advantage), and it may well prove sufficient for my needs. Should I feel like venturing into the realm of router flashing in the future, I'll have to look for a suitable router then.
For now, it's a job off my (lengthy) to-do list!