Yes you can.
The previous (2002) TSRGD only allowed a single vehicle type symbol on a parking plate. Clause 15(a) of Schedule 4 Part 2 of the 2016 TSRGD apparently has the same restriction (it only permits one of the symbols from Part 5). But Clause 18(1) allows you to combine any two types of parking on the same plate (without the need to duplicate the “P” symbol).
This interpretation is reinforced by the fact that when “type of user” is expressed in words, rather than with a symbol, more than one such type is permitted.
So my reading is that what you propose is permissible.