Out of time?

We filed an individual tax return for 2009-10 on 24 Jan 2011 (in time). HMRC wrote to us on 10 Jan 2011 (just about less than 12 months from actual filing date) giving us notice to check that tax return and requesting documents. The letter gives us until 14th Feb 2012 to send these documents. A formal statutory notice under Schedule 36 FA 2008 requesting information is expected come after 14th Feb 2012 if we fail to meet this deadline. This should give us another 30 days to collect the information....but:

Is the revenue window to raise an enquiry valid? Are HMRC time barred to raise an enquiry here? Is it possible to agrue that the the notice of 10th Jan 2012 is not a formal notice of requesting information and any subsequent notice requesting infomation coming in after 12 months of filing date is time barred as it is after 12 months of the filing date?

Thanks a lot.

Faisal