how easy to change st200 esp rear bank pass side i thinks theres one stickin?

Never changed one myself, so I can't answer that part of your question...

However, as hydraulic tappets are one of the most vulnerable parts to lubrication issues, have you considered that there may be a solution(/work-around) in a can to this problem?

Firstly, when does this happen? A problem at cold start probably has a different cause from a problem when the engine is really hot.

When the engine is hot, the problem is likely to be with low oil pressure as the oil viscosity decreases. If this also does not occur immediately after an oil change but gets worse as the oil has a few thousand miles on it, that would also be a sign of low oil pressure. Something like a 5w-40 oil or a can of the very gloopy oil additives (Wynns/STP and others) could help this, but the cause of the low oil pressure is likely to be in the bottom end of the engine, which sounds expensive/painful and unusual.

If this problem occurs for the first few minutes, or less, after starting and particularly after the engine has been standing for an extended period, then it is probably an oil flow problem, with oilways being 'crudded up'. A change to a nice, fresh, lot of oil would be advised, and it has to be of a good quality. Any oil that is also suitable for Diesels is likely to be good, because diesel oil has to be quite solvent to cope with the amount of crud that exists, but, in particular, I'd be tempted to try the Mobil Ford-spec Super 3000 (M1 would be good also, but is more expensive, and has the reputation for being very solvent).

Because of the limited tolerances in the hydraulic lifters, it is very easy for them to have small bits of crud that cause the seal to be imperfect and the pressure to leak away. This effect is more likely to last a whole journey, rather than coming and going as the engine warms up. Again, clean oil may help.

There is also a Wynns treatment specifically for hydraulic tappets, but, I've looked at the can and can't say which of these problems its supposed to cure (all???).

It might also help to give the engine a flush. I'm a bit loathe to recommend that, as, in some cases, it may do more harm than good, and, if an oil change, or more frequent oil changes may do the business, why not do that instead? But, if it is bad, a flush may be inevitable or just quicker than oil the messing about.

at idle quite normal tappty noise but when reved engine warm www.youtube.com/watch?v=p2cCvw5tTe0

if link works

oil change did not help tappit sounds are less noisy but when reved engine knocks at front ,looking like I,ll have to scrap the car as I can t go on like this