Not wanting to rain on your parade Murraymint, but its not screaming "tune me" is it? and 175k miles??? autotrader is full of high mileage petrol Bora's at this price. Clean it up, sell it, make a couple of hundred quid, save the money you were spending on the 1.8t conversion, buy a mk4 golf tdi with a great engine and monty's already on and without a boot and ugly front end and away you go.
Theres a reason why the diesel mk4's hold their value and the petrol ones don't.