Good afternoon 
I guess this is going to be a slightly complicated question, in a way, as I have no idea where to begin. We can't discuss it with family or friends as we want it to be kept completely secret.
Myself and my fiance are planning on getting married, entirely secretly. It will be at a nearby registry office, although not the same town and only a 15min drive. We want no guests, not even our children (all 12 and under) and we are going to ask the registry office staff for local hired witnesses. We don't really want any vows, we won't be dressing up much other than us both looking smart. We aren't having a meal or anything afterwards. Literally just go in, sign the papers and get back home in time for the school run. We want it in the week so we don't have to find a babysitter, as we never go out so getting someone to babysit would be completely out of the ordinary for us and people would start asking questions.
My questions - How much would it cost roughly for the notice, ceremony and certificate?
Are there any other necessary costs I haven't thought of?