458 2012 tried lowering but locking collers are seized uk

Where are you? I would go to your local dealer - I assume it is already being serviced under the 7 year scheme.

 

I know of one guy in Yorkshire who had the same problem took it into the garage to lower and they were locked tight so replaced. Dont know how you stand if you have already had a go yourself though.. Mine were really hard to move but soaked them in WD and they eventually gave in, apologies if a silly question but you did have the spring compessors on?

 

There are a couple of things you can do. First, a good rust penetrate will be your first step in getting them free. Second, you could try paraffin wax after the rust penetrate. In my experience, the paraffin wax works most times by warming the surface and melting the wax into it allowing thorough lubrication. Lastly, and this is a last resort, you could use a little propane torch to gently heat the collars. You HAVE to be careful doing that as obviously the shocks are filled with gas, I would NOT recommend doing it yourself and only use a last resort.