I already have a 30mm wire armoured cable within a conduit going to the shed this was for my previous shed for a light only,
However I have built a new shed and would like to wire a consumer unit in the shed which will power a lighting main and a socket ring main.
Currently the other end of the wire armoured cable is fitted to a socked in to the kitchen, I was proposing to connect this now directly to my consumer unit within in my house,

The shed will be used to power 15 fish tanks, a small heater and lights,

I would like 12 double sockets in the shed and 3 lights

Would this work?

What do you mean by 30mm? If 30mm cross sectional area then this is a very hefty bit of cable. If you mean 30mm thick then it means nothing. If you look here you will see there is a whole range of SWA cables. BS6724 SWA/LSZH Cable IEC60502 600/1000V and BS5467 SWA/PVC Cable IEC 60502 600/1000V are both SWA but current carrying capacity is very different. Two core to twelve core also means huge variation in what they can carry. And installation method will also change what it can carry.

At two core 29mm diameter we are looking at 70 sq mm cable some how I don't think one could ever get that into a 13A plug. So there is something wrong.

Thanks for that. The cable is est 30mm thick with 3 cores (Red, Blue, Greem) Iam not an electrician so unsure of rating of the cable but the inner cables just fin to a 13a plug,

The cable is SWA Armoured Cable 4.0mm 6944X 4 core would this be suitable to power all my equipment above

4mm cable is rated with consideration to where it runs and what it is made from so could be anywhere between 17.5A and 37A likely it will be protected with a 32A MCB or 30A fuse. But also there is a problem with impedance and really you need to measure the loop impedance before you can say what power it can run.