Cheers for the responses. I've had the intake problem as long as I've had the car. It's never caused a problem driving that I notice. It was only picked up at the first service at Peak Alfa but Roger reckoned it wasn't worth the considerable expense of fixing if driving wasn't affected. I'd have a crack at DIYing it with a scrappy part but unfortunately my long empty days of studentdom finish on monday and I start as a junior doc, I need the car for work so I won't have much time to get the car to a garage let alone consider DIYing it.
I can't see or hear any noticeable blowing from the exhaust but wondered if a small defect might have some impact.
The local 'Bosch' garage are charging £50 for the diag which I'd rather not pay but I need to get it sorted ASAP if at all possible.