Hi Malc, I did post last night while away from home but it looks like it has disappeared into the ether.
I only had a quick look at the kits and you have obviously done some research.
I have looked again paying attention to your intended use and accept that for any track use the suspension needs upgrading, how to do it and how much you need to spend to get the desired results is the problem that needs resolving. Lets look at what they offer.
1- Frontline.
Basically an uprated damper kit. If there is any weight reduction I doubt there is any worthwhile unsprung reduction where it matters.
2- Moss.
Plenty of waffle on the link with no detail. Looks good but this

. The road springs are retained by collars on the dampers allowing the spring and damper to work together..

Means nothing.
3- Hoyle.
From an engineering point I like it but IMHO it misleads.

the springs are positioned closer to the wheel enabling a much softer spring to be used

And you appear to have misunderstood this sales speak.

the Hoyle kit also move the spring outboard allowing a reduced spring rate because the lever effect of the lower arm against the spring is reduced.

As the sprung to unsprung weight has remained the same the spring has effectively remained the same the same. You may understand that but lets explore the sales speak.
Because the spring is further out it compresses more lets say twice as much (to explain). If the original spring was 100lb per inch and 1inch wheel movement compressed it ½inch it is seen as a 50lb per inch spring. Moving it out so as 1 inch of wheel movement equals 1 inch of spring movement to keep equilibrium you need a spring rate of 50lb per inch and nothing has changed.
It also states

and together with high quality damper units results in a more supple suspension

So we are back to the main improvement the damper.
4- MGOC
Uprated damper with camber and castor mods.
5-Uprated damper.

Im still of the opinion that for the money the main improvement comes from the damper.
Lets address camber it can be modified to suit by elongating the outer bottom wishbone hole and welding washers on in the desired position.
As for castor I think it depends on your driver feedback and is also easily altered by packing the subframe.
Anti roll bars?

I have tried to correct my last post as it looks garbled, the quotes were highlighted when posted. I have now tried 3 times with different browsers to post, all rejected as spam.