The next developments on the suspension front will be to fit stiffer front dampers and a thicker anti-roll bar. The car currently has standard Sovereign dampers which are soft, I've an uprated pair from my previous 4.0L Sport variant. I've also a thicker anti-roll bar from an X300 XJR along with new D bushes and droplinks to fit. I've been doing some hard driving recently and the car does handle much better with the lowering springs fitted, these additional modifications should improve things further.
The brakes are another area that I'll be turning my attention to. They do seem to be working reasonably well though I am getting a “low brake pressure” warning from the digi-dash indicating the system is not in optimal condition. The '86-'89 XJ40's have a complex hydraulic brake system which although very good when in fine fettle has proved to have unreliabilities. The pressure accumulator sphere has a nitrogen filled rubber sack inside which leaks and loses it's ability to hold pressure over time, I suspect this part is failing on my car. There are other parts which can be unreliable too, so one solution to bin off the standard hydraulic systems and replace it with a conventional vacuum servo. There is an American outfit which produces a kit of parts to enable an '86-'89 car to be converted, I'm planning to go for this as it promises to be more reliable and improve efficiency and pedal feel too.
Also on the braking front I have the braided hoses to fit, I'll take the opportunity to change the brake fluid for something decent. I'm also on the look out for some drilled/vent front discs too.