Drill the heads off, take cover off and drill the remaining bit of the bolt out and re-tap the thread, not easy, or fun, if you can't do it, find a garage or someone who can m8
Yeah probs the best way to take to garage seen some drill bits that say they take them out but not sure
Yey rolson! There's a brand you don't trust, they used to make zippo style lighters back in the day, now they supply all sorts of shit, I got a rolson rope and a couple of slide knives, I think they supply tesco with there cheap packet of random stuff too, 10x pack of super glue etc etc, yeah take to a garage buddy
dont dill and tap get some mole grips on them and some wd40 you may need to file two flat spots for them this has saved my ass afew time's
if you have access to a dremmel, grind a slot in the heads and use a large flat blade screwdriver in there. Another way is to drill just the heads off ...when thatyr gone the cover will come away leaving a thread sticking out. You can then get moles on that to turn it out or stud extractor if you have one the right size. Also, If theres enough thread left after the above method and you dont have a stud extractor, wind a nut on the remaining thread and then wind another nut and tighten against the first..then wind the first nut out using the second as a lock nut...it'll bring the stud with it
get a file and flatten either side of the bolt head then get the mole grips on them plus you want a plumbers blow torch. heat the casing around the bolt for about 30 seconds then stick the mole grips on and get turning the outer casing will expand quicker the the bolt inside freeing it up but dont heat it for to long or they will both expand. ive also done it with a hair dryer in the past but you have to heat it a bit longer and the misses goes mad when she catch's you lol
Heat the bolt heads NOT the casing, hammer an under sized socket onto the bolt (try an AF just below the metric size) do this while the bolt head is still hot and it should move with very little force. And great advice dont buy rolson tools if your serious about mechanics save up and buy halfords pro they are guaranteed and cheaper in the long run. Moles in this instance not recomm an impact driver best as it shocks the bolt off even "footprint" grips are much better.