Due to wanting less of a gap between the top of the tyre and the bottom of the arch I have bitten the bullet and bought a pair of 16" wheels and tyres for the rear, trial fitted them and the only issue is that the rear of the car sits high and the tyres stick out a bit (sort of Carlos Fandango style).
Happy with the wheels and will be sourcing a pair of 15" wheels to match for the front end (think the 16" on the front would be a bit over the top).
The up shot of all this is that I will need to lower the suspension, what is the best way of doing this? I know I can lower by reducing the pressure in the hydro system but the MGF lot suggest that lowering the pressure in the sphere's can result in damage (don't even know what the pressure should be for a Rossa anyway). but they do mention lowering knuckles. Anyone had any dealings with the lowering knuckles, how much lower can they make the suspension go and where can I get some from (will google the last bit but if anyone knows of a good place to deal with that would be good).

As you lower the car watch the wishbone angles. You are moving them out of their designed range of operation.
Also keep an eye on the angle of the driveshafts.

Another thing to consider, is that Talon will "individualise" the hydrogas for each corner, which would mean that you could set the height of the car and the corner weights better.