S2K-Phil

Not sure if this will work in your situation, but if you can turn it in the opposite direction first, even a very small amount, this can 'break' the seal between threads. Other than that get this: Max CD

heymynameismark

Plusgas, few knocks with a hammer, more Plusgas and try knock them free a little with a steel punch, as soon as you get any movement, soak in Plusgas again, go for a cup of tea, return, continue.

Fatbloke

Phil, as ever, it's hard to put a value on your contribution.

Mark, I don't drink tea. Is this a problem?

heymynameismark

Please insert beverage of your choice.

Nick Graves

Anything sugary will only cause the nut to stick further, though.

CynicG

Have you tried pi55ing on it? I heard that works. Although that might be to access frozen door locks, I forget...

Fatbloke

No I haven't, but you know that residue on your radiator last night? Well.........

tobyCHIPPO

Massive pair of water pump pliers and don't be scared at the collars being scratched/mangled.

CynicG

Touché

Fatbloke

Won't lose any sleep over a bit of mangled metal.

Currently bathing in plus gas until I've got a free moment to have another go at them....

Any suggestions for stopping them ceasing up again? I was planning a generous helping of spray grease, although I guess that means grit and grid will stick to it.