[rgwm]

If at the back of the arch, could be from the alarm/central locking box....is that still there?

Changing the pump should be easy enough if you have the arch liner and the top cover off...in fact you can probably do it from on top - pump is only held to the bracket by 2 x 10mm (IIRC) bolts, and of course the pipe connectors and the electrical connector.

 

[rgwm]

Put the inner arch cover back on, remove the reservoir cover so that you can still access the pump to "tap" it if necessary, and try it......but I bet you'll need to sort the bushes sooner or later.