I am paying £16.99 for Unlimited on a Market 1 exchange. It is the same price that I have always paid for Unlimited. Whether that includes a surcharge I do not know but I was not aware that I could save on the base price of the Broadband by moving my line to Plusnet.
However, having just gone to the product change page I see:
If you choose to take Plusnet home phone with one of our new broadband packages, you'll benefit from a £2.50 reduction on your monthly broadband bill for as long as your phone line remains with Plusnet.
I won't do anything about that at the moment because I will be re-evaluating everything as soon as Openreach complete the FTTP cabling which I am destined for. At that point I suspect that I will move everything to the same provider, either PlusNet or BT.