alan_m pretended :
I need to surface fix some plastic electrical trunking to a fairly irregular
surface internal wall. Would a grab adhesive be suitable for this
application or would I be better off drilling through the back and attaching
using screws?

Use the self adhesive type, but also drill and fix with screws to the
wall where there are gaps between wall and trunking. Fix at regular
intervals anyway, the self stick never remains stuck for long.