Price for PSE for 981 is £1473; I don't think it will be essential (see below).

I think you will be OK without PASM on 19" wheels (which are now 40 profile instead of 35 on the 987 19" wheels). I am doing the same.

I drove a 991 C2 Cab Manual last weekend for about 150 miles .. no PASM, 19" wheels. Standard car apart from heated seats, telephone module and rear park assist.


Amazing car. 3.4 engine is very eager and willing, and more than powerful enough for UK roads.
 

Gearbox is much closer than usual as it's higher up. Shift quality is good, if a little detached. Shifting from 7 to 3 is not easy to get right. Apart from that, I think you will get used to it.
 

Pressing the SPORT button increases exhaust noise and rortiness .. I tested this many times, and yes, the exhaust note (non PSE car) becomes rortier and louder in SPORT mode. In SPORT mode, exhaust is similar in volume to 997 Gen II PSE on.

 
Chassis and ride was beautifully compliant. Handling was much more 'alive' than the C2S PDK with PDCC that I drove last year. You feel the car moving around much more, and for me, it is more involving, more interesting and more effort to go fast round corners. Ride on our nasty roads is really beautifully controlled. On really horribly worn sections of the M4, it jittered around a bit and felt slightly unhinged, but that's it.