Life imprisonment in the UK is (or used to be) 20 years. But that's just the starting point. A minimum tariff is then imposed - this could be less than twenty years and could also be more than twenty years (Ian Huntley the Soham murderer had a minimum tariff of 40 years set)
The minimum tariff means that's the minimum length of sentence they will serve before they are eligible to be considered for parole. Not many get parole at their first attempt either. If they do get parole they remain on licence for the rest of their life. Even the slightest thing can mean they're returned to prison.
In some cases life really does mean life for the worst murders so where murder is concerned I don't think the UK does too badly where it's sentencing is concerned.
Wouldn't there would also be a possibility for him to be transferred to complete his sentence in the Netherlands (I know I'm getting ahead of myself in terms of guilt, but I'm interested in exploring the possible outcomes)?