Your solicitor will apply to the court to have it granted. You don't need to do anything except sign it when it pops through your door then post it back to your solicitor for him to pass to your ex (or his solicitor) for him to sign and that's that.
Mine cost me sod all because I got my ex to arrange it all, it cost him �60 plus solicitors fee's.
We did the same as you - got the legal separation, split our assets and went our separate ways, divorce was granted 2 years after the legal separation.