Well, it turns out that at prolonged high revs the alternator was kicking out more than it should have been - I have now tracked that down to a faulty regulator which I have replaced.

I have also now constructed the means of fitting an air filter (piece of drain pipe and bit of cigar tin...)

It seems to be running much better now, though it was still struggling with hot starting - getting there slowly!

Hot start probs will be either tappets needing gapped or Im afraid coil again - if they have been overheated once the varnish on the LT winding wire will be damaged and so the coil will be prone to poor performance when it starts to warm up.

This just seems to get more and more confusing!

I have tested and adjusted the regulator so it never runs over about 14.2v (and I have a volt meter on the dash so I know it has not), then fitted my new coil from Ecas ("our coils will not be dead out of the box" or something similar as it says on the website).

Well, it started and ran fine... for about 20 minuets... then started acting like an over heated coil, put my old coil back in and started first time (and ran for about 20 minuets again).

So... I tried fitting my (second) new set of points and condenser. Went to start it, it spluttered twice and then did nothing. I tried both coils, checked the pugs are being sent a spark (with a strobe - and it was though it was a bit dim).

I then tried pulling the plugs out as I thought it might be flooded - and this is where it gets really strange... one plug was sopping wet (as expected) the other was bone dry...

Any thoughts, suggestions or similar - I swear someone is testing me!

... one plug was sopping wet (as expected) the other was bone dry...

Hi tev, tried adjusting the valve clearances? Your motor started easily from cold at the last WASPS meeting though I noticed it was uncannily quiet i.e. I couldn't hear any chattery tappet sounds.

I have checked and re-checked them, I supose I can check them again... 20 for inlets and 25 for exhaust if memory surves me right?

Sorry to suggest sucking eggs but did you check exhaust valve clearance with opposite exhaust valve open, same with inlets?

As there is clearly an imbalance then its more likely to be something specific to either cylinder. As fuelling timing and ht are all siamesed then, whatever is happening for one cylinder is happening for both.
Tappets as bugtster said should be done with the adjusted one being set while the opposite is fully opened.
then its compression to make sure they are both similar and that one side isnt nipped scored or worn.

HT leads and plugs fine? and a strobe tests the timing not whats happening with the plug

What ignition are you using ? oily connections and or a tired battery makes 123 fire one sided
and oily stuff makes the condenser fail on conventional set up which either stops the ignition working cold or gets progressively worse as it warms up, for all the world like a diuff coil.

Have you checked the inlet manifold gaskets are ok? sounds like it may be sucking air in and mis firing. When its cold it runs ok but after 20 mins everything expands due to heat and then it starts acting up, worth checking and just my 2p's worth.

As I read this I guess you are driving with original points and condenser; do you have the right distance between the braker points 0.4mm? When this isn't
right your car would behave great when cold but when the coil heats up by getting always to much current it will sputter and do more nasty things...
so please check this.....

Yes, valve clearances checked corectly, though may do again tonight just to be sure!

HT leads and plugs nearly new, though dry plug is quite sooty.

I know thats what a strobe is really for, but I just wanted to check it was actually trying to spark - tbh I suppose holding the plug on the engine would have done but meh... I didnt think of that at the time!

I am wondering if I have a faulty or erratic valve, is there any easy way to check for this without dismantling the engine? Atleast this is the only reason I can think of that one plug would be wet and the other dry but neither atempts to fire! Both cylinders seem to have some form of compression (though I have no idea as to how much, seems as I dont have a compression tester it was down to sticking a finger in the hole and checking it was trying to compress!)

Ignition is points and condenser, I believe it was / is set correctly. I am a little annoyed with myself that before I replaced them I didnt try starting the car to make sure it was working, as now they have been replaced I dont know if its just a faulty new condenser or something causing it to not start. May put the old one back in to check I supose.

I have been round the manifolds with a tin of WD40 and didnt seem to be any signs of it leaking.

I am wondering if I should just give up and swap it for the spare engine I have sat at my store - My main fear with that is if the problems would persist (though I suppose that would at least show it was an electrical fault!). On that note... is there any way of getting an idea how good or bad an engine is likely to be short of firing it up? I have 4 in total (including the one in this car), the other 3 turn, but they look pretty ropey and I havnt had any of them running.