In Austria and Switzerland military service is also compulsory, but not really because of defense (Austrian military is a joke if push came to shove), but because it's an vast source of free labor for the state.

Unless you decide to go full career in the military, once you're done with the month long boot camp, if there's no war, national crisis or natural disaster that will get the grunts mobilized, the rest of the 5 months of service, are spent by the recruits dicking around on the taxpayers' money, doing useless busywork around the garrison.

And there's almost no way to avoid it unless you suffer from a severe physical or mental illness making you unsuitable for service, as even after you get out of prison for refusal, you'll be drafted back in.

PS: funny that you moved from Norway to London as many Brits I've met look up to Norway as a role model, so I'm really interest in your story