Hi Gazzer,
Here is the current HMRC form required when such a transfer occurs. The form itself is proof that such a transfer is possible.
http://www.hmrc.gov.uk/nic/forms/ca1881.pdf
Does your SIPP contain protected rights? I didn't think SIPPs can do this. Your SIPP manager may have said that your can't contract out of S2P which is true - you would need an appropriate personal pension to contract out. If you are thinking of contracting out for the current tax year, you only have a few weeks to do so.
As previously mentioned, the rules to transfer abroad change on 6/4/06. The link below refers to the section in HMRC's Registered Pension Schemes Manual that deals with the transfer of UK pension benefits abroad, if that is of any interest.
http://www.hmrc.gov.uk/manuals/rpsmmanu ... 101020.htm
Rgds
mkp