For 2.30 I would expect to see the groom at the ceremony for 1.30 but that very much depends on the nature of the ceremony venue, because a registry office can be busy with weddings it could be that arriving too early he may find he is mingling with the wedding before yours that are about to go in.
But that also depends how big the reg office is. Either way he needs to make himself available to be interviewed by the reg before the ceremony and before you arrive and then he can be out of the way for your arrival which I would expect to be around 2.15.
You should perhaps be ready to leave at 2.00. If it looks like the traffic is ok you can always take a short detour so that you do not get there too early.
So without knowing your venue its tricky to say, the best thing would be to ask them directly.
I have photographed weddings at registry offices where it was the first of the day and its all still closed up to 1 hour before.
If I was the wedding photographer for your wedding I would suggest the groom leaves at 1.30 and for you to be also fully ready at 1.30. This then means that I can get shots of both of you getting ready and the groom heading off. Then with him out of the way at 1.35 I can get shots of you outside with the bridesmaids/ Parents - if there, and a shot of you with the car, so I can then leave at 1.50 to get to the reg office where I can get shots of the groom and lads - his parents - other guests arriving. So we would need your car to be with you no later than 1.40 so I can get that shot before I head off.
Here is a link to my website starting with bridal prep with links to the groom and the ceremony that you may find useful. Leicester wedding photography