Need help for exhaust

My exhaust has started blowing badly and I have just dropped it off to the garage who have confirmed its the flexi-pipe on the manifold which has gone.

My current options are to buy a second hand manifold off ebay which I am already watching one or replace to flexi-pipe and they can weld it on.

I need to know what the diameter is off the flexi-pipe as there are loads of different sizes, if anyone knows or can measure up I would be grateful.

The garage dont know and cant access it without taking the whole thing off.