Not sure they are that keen. The base price for renewal of Infinity2 is £28 (seems to have gone up in the last few days?), £2 more
than for a new customer base price.
so costs per year are:
Old customer base price = 12*28 = 336
Old customer discount price = 12*24 = 288
New customer price = 3*20+9*26-80 = 214 (* but 18 month no 12 contract)
The old customer discount prices seem to vary a bit from day to day, and depending on whether or not you combine with line rental saver.
Also you probably can get cashback as new customer as well.
New customer gets an HH5 as you did (though seeing what people say not sure if that is better than modem+HH3 other than dual band wireless)
It certainly shows that as an old customer you need to contact them to get a half-reasonable price.
It looks for me that a move to PlusNet is going to be a good move; even though I'd rather stay to save the risk of a botched move.
Helped by PlusNet having a 40/20 service which BT don't have.
BT Infinity 2, thinking of moving to PlusNet