Again, thank you all for your help.
This was how the wiring looked before the refurb last year, the box had already been fitted by the previous owner and seemed quite new, and I'm sure it had a 16 amp fuse fitted.
After the refurb, my cousin and an electrician that he works with, who also happens to be his brother-in-law, put all the new wiring in for me. Everything seemed OK and I didn't have any problems, but there again, it was before I had started kitting the shed out. The first item I bought was a 50 litre 3HP compressor which I'd planned to use for spraying the walls, as it turned out I was pretty useless at spraying and the compressor was pushed to one side for a while. After I was ready to start building benches etc, and at this point the only things plugged in were the freezer, radio, phone and the Record AC400 air filter, I brought the compressor out, can't remember what for but every time I switched it on the fuse on the main board in the house would trip. If I turned the air filter off, the compressor was OK. I think this is when my cousin swopped the 16 amp for a 35 amp!
Once I had the work station built for the Bosch mitre saw, I bought a Nilfisk 30T 1800W vacuum, hoping the Bosch would work off the Nilfisk, but every time I switched the saw on, the fuse in the house would trip again. The Nilfisk went back to the shop, and I think that was then the electrician came back and replaced the RCD. During all this time I'd used the Axminster TS200 connected to the Lidl's vacuum cleaner without any problems.
Leading up to my original 16 amp question, I mentioned to my cousin a couple of weeks back that a few of the planner/thicknessers I'd looked at required a 16 amp upgrade, that's when he swopped the 35 amp fuse for the 40 amp. I switched pretty much everything on in the shed that wasn't already on, radio, phone, freezer, six strip lights, AC400 air filter, BS350 bandsaw, 1800W mitre saw, the BIG Triton router, and a 750 belt/disc sander, the only thing I didn't switch on was the table saw and vac. Just in case!
I'll try and find out tomorrow if the sockets/breaker are on a ring!
Pete.