Well, if anyone has read my last few posts,you would know that I had a serious loss in boost. About 2 months after the remap my power dropped to 0.4 bar. The mechanic that did my service was not particularly useful, to the point where he said there was nothing wrong.

Ordered the DV - known as a cut off valve - on Monday and had it fitted this morning by an independent. Power is fully restored. After driving it for over a month with loss of power I forgot how fast this thing is! Absolutely chuffed to bits

Big thanks to all those who offered advice. Seriously folks had it not been for this forum I would have been lost. The dealer would have taken a lifetime to fix it and would have charged me a fortune. Instead it cost £28 for the part and £30 to fit it this morning. (Carworks NI if anyone in Northern Ireland is interested)
Big thanks to vrstu who gave me the part number.