What type of Cable

I am in the process of putting some Electrics under ground to my shed from the house it's a total of about 25metres, could any one advise of what cable to use? any the best way to do it

i would reccomend a 40A cuircuit

while this is overkill for your present requirements you really don't want to have to dig that trench twice

the biggest issue fotr cable selection in theese kind of installs is voltage drop

for a cuircuit of this rating over this distance 10mm 3 core SWA is the cable i would reccomend (6mm would comply but only just)

while you can use 2 core and use the armour as your only earth connection i would generally advise against doing this especially for diyers

there are lots of different ways to do it all with thier pros and cons butmy reccomended installation pattern is

40A mcb in non-rcd side of house CU
short run of 10mm T&E
metal modular box with 40A rcd (this also allows you to isolate the outcdoor wiring completely if its damaged)
10mm 3 core SWA (terminated with appropriate glands)
metalclad switch only CU in shed
normal cuircuits for lighting and sockets

btw the armoured cable should be burried about half a meter deep (regs guideline is 450mm but i don't think being right on the edge of regs is a good idea) it should be protected from shar stones in the soil (for exaple by surrounding by sand) and cable warning tape should be placed above it. The cable warning tape should be out of the way of normal digging but far enough above the cable to warn someone before they dig thorugh it