.. I’ve watched the video’s, they just unscrew and you can replace the o-ring.. So why when I try to unscrew the ‘inside’ screw under the tap handle are they seemingly tightened by gorialla’s? I’ve already destroyed one, as not only was it tight, it was made of cheese, not to worry we need a bathroom make over anyway 🙄
The other is more annoying and in the kitchen, and relatively new, so why won’t it budge!
Any tricks, or am I buying a new mixer tap?

What sort of taps? ‘Normal’ ones or fancy quarter-turn ceramic washer type taps?

If it’s the normal ones, you can buy valve kits pretty cheaply. You just isolate the tap, unscrew the whole valve assembly (normally via a large nut which is part of the asembly) and stick a new one in.
They can be hard to get started, but a big adjustable normally does the trick!

TBH I don’t know because I can’t get the damned handle off (held in by this screw) to access the valve!

The “screws” on my mixer taps are allen key bolts with a decorative plastic cap that just flips off.Once removed the tap valves were quite stiff and needed a hand on the tap and some welly to unscrew.Replacement ceramic valves can be gotten from Screwfix or ebay depending on size,

I feel your pain. I too have a drippy tap but cannot unscrew it to fix. I can get the cover off that exposed the brass screw, but will it budge..no chance, not even wd40 helped, and being recessed about 2cm I cannot get at it either. New tap time me thinks.

The screw are made from brass so very soft drill the heads off and the handle should pull off.
Then get some new valves.

Cheers, that sounds possible though more of a mission than I’d hoped