MrP. A man of your experience should know not to enter negotiations making it quite so obvious that you're desperate to buy!
That said, hope they can!
This upgrade is only available on the 310R, Ti-VCT Sigma engine. The reason being is that the engine already has a lightweight "billet" flywheel and performance cams making the upgrade more financially attractive at entry level than the entry level Fixed Cam Sigma upgrades.
We do offer the F155 upgrade for the earlier Fixed Cam Sigma which gives between 155 - 160bhp. We really wouldn't recommend going any higher than this on a standard flywheel. Our F175, F190 and F200 upgrades are only sold with a billet flywheels. The standard cast, heavy Ford flywheels have been known to crack.
The best upgrade you can put on any Sigma engine is our ultralight flywheel and clutch. This is 5 - 6kgs lighter than the Ford flywheel and about 3 kgs lighter than the Caterham lightweight flywheel. If you've driven with a heavy flywheel before, fitting one of these, gives the impression you have loads more power, when in fact you don't. It really brings the car alive, making it more sensitive in corners, making it easier to steer with the throttle. It also makes for much faster gear changing and greatly improves throttle response. You could go for this as an initial upgrade and drive this for a year or so and then come back and have the F155 or F175 upgrade carried out at a later date.