Thanks to Dove's Vauxhall in Southampton I now know what is causing my P1112 fault problem. I have replaced the Swirl Flaps & also replaced the MAF sensor at a total cost of £450.
But, after having Dove's use their Tech2 diagnostics it is the Swirl Motor malfunctioning. They quoted me £650 for new flaps, gaskets, motor, fitting & VAT.
However, as I have already replaced the flaps I only need a new Swirl Motor which I can get for £150, then get my local garage to fit for a further £150, so £300 then finally I will have an end to the P1112 fault.
At least I have now learnt that if I get any more fault codes to get the car linked up with Tech2 before wasting more money which could of been used to repair the actual fault in the 1st place.