Yup they were still doing it last year, a friend had his night rating added in this way.
I'll be going to Gatwick to have my Multi rating added mid-July. You should get to the CAA offices as early as possible and they will take all of the paperwork, licence, logbook. payment etc. Then they'll give you a time when to go back to the office later in the day to pick your new licence up.
Just a quick question. Would it be easier to get to Gatwick from Redhill rather than Biggin Hill?