You are best to use CAT5 cable, and make sure you use a true pair not any two wires.
The commonly used pair is Blue (possibly with white markings) with White+Blue markings.
If you do use phone cabling it needs to be CW1308 and twisted pairs, as the others have said. Cheap, flat, untwisted pair cable is not recommended.
The reason is that any wire can be subject to external interference. The two wires of a twisted pair get affected in opposite ways, so to some extent self-cancelling out the interference. If you use untwisted, or two random wires that aren't a matching pair, the interference is reinforced rather than largely cancelled.
Don't mess for the first 3 days. By then the things that actually control your line will have decided what to do, though you may get a few decreases in speed after that. You won't do any harm as long as you make sure you wire it up correctly, as above.
The 10-day period is/was basically to do with the BT Wholesale recording of the lowest sync speed on ADSLx
in order to set fault reporting criteria. On FTTC all the BT Wholesale DLM seems to do is set the IP Profile. The line setup itself is by the Openreach DLM. The fault criteria are totally different - and pre-determined. As is what the OR DLM does about instable lines. It doesn't use the Noise Margin settings like the BT Wholesale ADSLx system. It uses speed bands to limit the maximum and minimum sync.
My broadband basic info/help site - www.robertos.me.uk
| Domains,website and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 54.2/15.2Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.