I just emailed them to find out what's going on. Mine has also been put back by another 3 months. Although this of course is a holding date and means it could be any time in the next 3 months (unlikely) or it'll be pushed back again around this time in 3 months
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The annoying thing is that I only ordered BT Broadband originally due to the soon to be available Infinity (31st December 2011) and ever since then it's been pushed back. 3-6 months I could have accepted without grumble but it's becoming a farce. Especially as I'm fairly sure it's been cabled up for over a year now and the cabinet has been down for the same period. Additionally, a 2 minute walk down the road to the adjacent street and they're available to get Infinity.
Rang them to check on the off chance that the online checker was wrong and definitely not available