If you were able to place an order then the answer is presumably "yes" but there's some short term problem.
For sn1 4nb the postcode checker says no, but it isn'[t great.
For number 6 the address checker says it's available ....
Address 6 VALLEYSIDE, SWINDON, SN1 4NB on Exchange SWINDON is served by Cabinet 21
WBC FTTC Up to 57.8 Up to 20 -- Available
MaxDSL - goes as fast as it can and doesn't read the line checker first.