The last 2 evenings I've spent fixing my mums 1242cc 8v FIAT 500. I noticed a little blow on the exhaust and on closer inspection 2 of the studs were missing from the manifol, and when I looked further they had actually snapped off - in the head

God know how this has happened as my mum bought her car from new and its only ever been serviced by FIAT or myself. Exhaust manifold has never been removed. FIAT weren't interested and said there had been no recalls concerning manifold studs.
I did quite a search on the net and there didn't seem to be much in the way of guides for the 500, so here's a quick summary for those that might find a similar fate.
The 1st night was spent removing the manifold, but as access is pretty terrible with a drill (and a 90deg bit) I then decided to remove most of the front end to make things easier meaning a late finish.
In order to do it you need to remove the bumper. There is a guide on youtube already, essentially 4 torx at the top of the bumper, 3 underneath, 1 in each wheel well and 3 screws. Disconnect the DRLs (and foglights if fitted) by pulling away the plugs. The number then pulls out away from the wings.
I needed to remove the radiator to get a straight view of the manifold studs, so here's what I did. Remove the airbox and little inlet pipe - 2 small bolts from above and 1 hose clip for oil breather. Rear hose just pulls off the air filter etc.. There should also be a small bolt/screw which holds the air inlet pipe onto the front slam panel.
Remove 2 large front cross braces. These are each held on with 8 large bolts and 2 small locating nuts.
Once these are out of the way its time to get to the radiator. Unbolt the air con condensor (4 small screws in each corner). There's 2 small screws that hold the fan assembly to the radiator from the other (engine bay side) side. With those removed you need to unclip the 2 electrical connectors. Pull the fan shrouding upwards. The radiator itself has 2 large coolant pipes to disconnect, and then 2 mounts at the bottom which are bolted to another crossmember with 1 bolt each. Remove those and the radiator can be lowered down and removed.
Onto the manifold! Undo the lambda sensor and put it somewhere safe. It also clips through a small bracket attached to the rocker cover/head which can be removed to give you a bit more space. Next up there are 4 small bolts on the heat shield and 2 nuts at the top. Pull heat shield upwards and remove. The exhaust manifold is held on with 8 nuts onto the studs in the head. Remove all 8 nuts. There is then a single large bolts which holds the downpipe onto the mounting bracket underneath the engine. With this removing pull the manifold out and lower down - the whole exhaust will drop down and you now have space to do whatever you like.
Around 8 hours later and I'm exhausted. The exhaust studs wouldn't come out for love nor money, using multiple drills (including reverse thread) of varying size and some easy outs. I eventually opted for using a helicoil type set and its as good as new (mate x 1.25mm if your interested).
Chris