Can I install a new light switch from a 3amp fused box

[Rawsox8]

Want to install a new permanent fixed wire light into a 3amp box.
Box has my new combi running from it and that's it. It's a wardrobe cupboard where the old hot water cylinder lived. Box is wall mounted and 3amp fused.
If I ran a 1.5mm twin and earth from it to a new light switch and then connect that to a new batten light fitting. Would that be ok?!

Or should I go into the loft move all my partner's crap in boxes away from the joists where the ring circuit lives and tap into that with a 3 terminal junction box?! And divert that to a switch and batten?!

I'm hoping the 3amp box is the way forward! Quicker and easier for me Haha.
Cheers

 

[littlespark]

Your first idea. You can easily come off the same supply as the combi... with the 3A fuse protecting the combi AND your new circuit... Then go to a simple one way switch, then up to the light.

To take power from the RFC you would still need to fuse down to 3A. Unnecessary extra work.

 

[Rawsox8]

Your first idea. You can easily come off the same supply as the combi... with the 3A fuse protecting the combi AND your new circuit... Then go to a simple one way switch, then up to the light.

To take power from the RFC you would still need to fuse down to 3A. Unnecessary extra work.

Perfect as I thought. Just checking all the regs are good for it.
Cheers for that