Advice please on small garden room spur job?

Good afternoon folks,
We have what i suppose is a small consumer unit

Good afternoon folks,
We have what I suppose is a small consumer unit in our garage (with RCD breaker) on its own feed from the main consumer unit in the house (by which I mean it has its own switch on the board). This in turn feeds supply to a couple of sockets, garage door mechanism, lights. I want to run a new supply out to a garden room nearby, and I propose to run a length of 6 mm²  SWA 3 core armoured cable to the garden room, directly into a double 13A socket (well I'll probably do into a junction box and take internal 3-core off that) with a 6A fused spur leading off to supply a single light and switch. Can I get away with that or do I need anything else? I'm assuming I don't need another fused spur before the socket for example?
Kind regards Bob

Depends on cable run lengths and size of cable supplyig the garage - need more info.

A 6mm  armoured to a garden room  is a bit big  considering the load .   Or is it 5 miles away  from the garage ?    Or will you be cooking in there ? 

Can you tell us  the  length of the cable run ?  

I can almost guess that your load will no more than 2KW    So  work on a 10A load  max.