As fare as I am aware they are removable without the bumper coming off(a tad fiddly, but possible) and they also don't require the system to be degassed prior to removal....
I will look rather silly now if I am incorrect, but sure someone will save you a hissing front end and me removing myself from any forums!!!!!!
Providing the pressure switch is not corroded onto the threads of the valve it is removable. Sadly half of mine is corroded immovably onto the threads to the point where efforts to remove it are beginning to twist the pipe rather than any other progress. I have at least two tools I have tried to use that would work if it wasn't stuck - crows-foot spanner attachments for a 3/8 drive small breaker bar, and a hinged plumbing tool, both of which can be inserted behind the bumper moulding from a foot away at a shallow angle to grip onto the hex portion of the switch and twist it.
Just wondering if it is possible to fit an air con pressure sensor in a different, more convenient location and extend the wiring through a suitably made matching male and female plugs.
If the sensor could be relocated onto the high pressure servicing point next to the expansion tank and about a 3 foot extension cable to fit between the existing connector in front of the radiator routed past the ABS pump up to the servicing point MAY work. You may need a short adapter on the charge point or perhaps a pressure switch from a different model. Make sure you also use a suitable o ring to seal properly.