Yes you should be able to use X11 with an Option E PSC. The primary purpose of X11 is to introduce termination at will in addition to the other grounds in Clause 90.
The Calculation would be carried out under X11.2. In other words, the terminated professional would receive 5% of the difference between the estimated total of the Prices (this would be a forecast of the total of the Time Charge under Option E) and the total of the amounts due on termination. Put simple 5% of the outstanding work value.
The Calculation would be carried out under X11.2. In other words, the terminated professional would receive 5% of the difference between the estimated total of the Prices (this would be a forecast of the total of the Time Charge under Option E) and the total of the amounts due on termination. Put simple 5% of the outstanding work value.