If you've used decent quality twisted pair such as CW1308 or better and kept it away from mains and other sources of interference then there shouldn't be much of a problem. It's attenuation at various frequencies that matters, not dc resistance, but interference pickup is really what it is all about.
I have zero metres of internal wiring, I got BT to do a 'change point of entry' to move the line to exactly where I wanted it, so each line (I have three) comes straight into the house right to my the modem, and then any extra distance that needs to be covered is handled by ethernet which is 100% perfect.
If you are desperate to get the best performance, then BT ‘change point of entry’ and zero internal wiring is the way to go. This means moving the point where the cable first comes into the house to be exactly where you want it, and that will be where BT will park the master socket for you, but for best results this really must have a (hopefully minimal) run outside the house not inside. Then for you to get the benefit you absolutely have to move your modem to where the master socket is, which is hopefully now at the first point at which the cable enters the house. My reasoning is that all house-internal DSL signal wiring is potentially suspect because of all the interference sources in a house from mains and mains-powered equipment. You ask the company that you pay your line rental to, your phone service provider (if you have one), to organise a BT engineer if you want.
If running cable through the house is a pain use wireless as that is 100% perfect (because of error correction and fast layer-internal retransmissions), provided of course that the signal is kept reasonably strong.
It is not necessary to have the source of your wireless network parked at the same place as where your DSL modem meets the incoming line. If you minimise internal wiring for DSL signal, you can have a wireless access point (base-station-transmitter which controls the wireless lan) on a long ethernet cable connected to your router and park it in a different place for better signal spread, such as in the centre of the house whereas your modem/router might be on an outside wall for shortest dsl signal run. This is all more inconvenience and nuisance running fragile ethernet cable though. This is how my wireless works. Modems are by a window on an outside wall upstairs, there is a pair of long ethernet cables from the router to two wireless access points in the exact centre of the house, one on each floor, to give a wide spread of signal. So wireless location for best signal reach doesn't have to be the tail that wags the dsl quality dog.
It all depends on how obsessive you are or aren't about dsl performance (more speed)and reliability, versus inconvenience - relocating kit, possibly booking bt - and a small expense - cost of bt poss, cost of a WAP poss.
I never my case I was extremely pleased with the results which were stunning, speeds went through the roof.
Don't hesitate to come back with any questions?