Sorry to go against the grain, but I wonder if you're making a lot of unnecessary work for yourself.

I wouldn't be pulling the engine unless it's got a large amount of kms, and you intend to reco it, or put in a low km engine - to which I'd change welch plugs, seals etc, before putting it in.

Have you tried nipping up the sump bolts, degreasing the area, and seeing if your leaks go away ?? If your leaks are not major, maybe you're better off living with them for the time being. Have you confirmed where all these leaks are coming from ??

You can do most of what you've described, while you have the head off - welch plugs, pull exhaust and inlet manifolds out. Rear main and rear welch plug can be done with your manual conversion. I agree that's a good idea to replace all coolant hoses (particularly the under manifold hoses which are probably 10+ years old), very easy if the inlet manifold is out. All these things you aren't making needless extra work, as they are now very easy to do.
I'm all for preventative maintenance, but if your engine isn't giving you any major problems at the moment other than what you've described, maybe you're doing too much.

Hope I haven't contradicted myself here . . .

perhaps i will give it a thorough degreasing and check all the bolts on the sump etc. and see how it goes.if i was to give everything a good degreasing and make it clean and oil free would actually running along the outside of the sump gasket with a silicon sealant would this do any good or would the oil simply leak past this?

you believe at this stage the welch plugs shouldnt be in need of replacing??

perhaps at this stage ill just plan to pull the head off and then asses the situation once the head is off and i can have better access to look around.?