Many thanks for taking the time to reply - cutting a ridiculos story short (you can't invent the madness that is TalkTalk customer service) - I currently have FIVE routers - all the same - all sent within 7 days. The OpenReach engineers router works first time out of the box - and he has been twice now.
Try telling TalkTalk that just sending more routers may not sort the issue and they send another router.
They make a loveley set!