( he also said that it may be too many things into the surge protector and i should get another one and split what i have plugged in so as to reduce the amount of appliances plugged in )
It's likely to be earth leakage current causing your 30ma RCD to trip.
(inside the surge strip are capacitors to earth which help with common mode noise, these leak current to earth)
The number of appliances plugged in doesn't affect the surge protector as it is plugged in all the time anyway.
As a test, leave the strip plugged in but plug all your other stuff into a normal extension, if it still trips then the SP strip is maybe iffy.
Remove the SP strip, if it still trips the RCD is maybe iffy, or something else is.
You may not actually need a surge strip because the basic noise/surge filtering is already inside all your devices, otherwise they wouldn't have passed any EMC tests.
...take a PSU apart, that little circuit with the blue and yellow things, that's
exactly what is inside your surge protection extension, you are just doubling up really.
Adding a few MOVs instead would provide supplementary lightning protection with less leakage compared to the CM caps. Mains noise reduction generally isn't of much benefit to a computer.
A medical isolation transformer would reduce the earth leakage issue to almost nothing, sometimes they pop up on eBay for £20-30
A CVT is the best solution for surge protection, about £100-200 on eBay
