Working out garage electrics

[AP77]

My house (built in 1989) has power supplied to the garage where there is a separate fuse box with a separate on off switch The garage fuse box says max load is 45 amps and there are 2 fuses in the box, one is 5 amp, the other is 15 amp.

From the 5 amp fuse I currently have:
3 fluorescent strip lights, 1 PIR light and 2 outside wall lights.

From the 15 amp fuse I currently have:
1 double wall socket

I am buying a wooden workshop which will be next to the garage and would like to understand what additional lighting and sockets I could add to the workshop and garage with this exiting set up.

How do I calculate the total amps that I will be using if, for example, I have 8 lights in total (6 in/on garage, 2 in workshop) and 3 double wall sockets (2 in garage and 1 in workshop and they are all on at the same time?

Thanks.

 

[ericmark]

Step one is to look at the Wylex fuse box supply. If supplied with 1.5 mm² SWA clearly can't have same capacity as if 6 mm² SWA. Picture does not help. And also if supplied from a 10 amp MCB in main fuse box, clearly can't draw 20 amps what ever it says on the fuse box.

The fuse box will need renewing for a consumer unit, as today new sockets will need RCD protection, and although technically you can apply to the LABC and pay fees then DIY, that will cost more than getting a scheme member electrician to do the job.