Moving to a house where fibre is slower than ADSL

[#1]

I'm currently on Plus.net fibre and getting around 60Mb download speed. I'm looking at moving home, though, and the new home seems only to be able to get 2Mb down on fibre broadband, presumably because it's far away from the exchange/cabinet. The estimated ADSL speed is 4Mb, which still isn't great but at least is better than the fibre speed.
My question is: will I be held to the fibre contract if I move (assuming I move within the minimum contract term) even though the fibre speed is slower than ADSL or will we be allowed to switch to an ADSL contract? I've got no problem staying with Plus.net - I just don't want to pay more for a slower product.

[#2]

There's something seriously wrong with those estimates. ADSL is home to cabinet to exchange, FTTC is home to cabinet only so the FTTC should always be the better. The only way it could be strange is if the cabinet is very close to the exchange but you are miles from the cabinet.

[#3]

I suspect there must be a mistake somewhere there, as if the line was so long from the cabinet that the fibre speed was that slow, then the line would be even further to the exchange, so the ADSL speed would be even slower, or more likely none at all.  I don't think BTOR will actually provide a fibre connection if they think it would perform below a certain amount (15Mb springs to mind, but that may not be right).
It would probably be worth pursuing the likely incorrect fibre speed than going to ADSL, I would have thought.
Phil
Edit: Jelv beat me to it!

[#4]

The minimum speed for BT Infinity is 15Mbps I believe so I assume that is a limit coming from BT Openreach and they won't supply fibre if the estimate is below that
Interesting question though I wonder if there is a database error as I have never heard of an estimate being that low

[#5]

I asked about this on the BT forums and basically the speed you get with fibre drops more steeply with distance while ADSL can carry further. Hence the ADSL speed for the property is faster than fibre because of the distance from the nearest cabinet/exchange.
BT don't offer BT infinity at the new place. They just say that fibre broadband is available, but at that speed they don't call it Infinity. Technically it is available. Just not worth having.