Progress!..albeit a month later as i've barely touched it since and have just been using my work van instead as im been too busy, skint and / or it's been raining so the opportunity to get out fettling hasn't arisen.
I ended up taking it too my workshop today where i managed to sand the remains of the sump plug off and then drill it out to allow the drainage of the sh!tty old engine oil before whipping the sump pan off so that i could drill it out properly, re-tap a fresh sump plug in and give it a bloody good scrub up!
New oil and filter followed which has smoothed things out a touch but didn't remove that horrible noise so further investigations ensued on all the moving parts on the offside of the engine.
With both belts removed completely I eventually pin-pointed it to the water pump bearings which is odd considering i replaced the pump about 18 months ago when I did the cambelt and major service. Must have been a cheap sh!t component but this aside at least i can rest assured my head isn't tw@tted now.

Something else i did pick up on whilst beneath the car whilst it was running was the faint and irregular rattle coming from the nearside end of the gearbox, behind the square end cover plate Im guessing? Any ideas?