roll cages.....

Any good tips on companies in Sweden that sell or manufacture these things ?

Cheers Simon.

Is it for the M3?

Anyway, a good company not to far from Göteborg is Gunnarsjö Svets och smide in Varberg. They're doing excellent jobs and prices are decent. Have a look at:
http://www.svetsosmide.se/

This is a very nice thread on the roll cage subject, including a list om companies:

https://rejsa.nu/forum/viewtopic.php?t=13250