In the end I changed the rear cassette and chain and have completed two return trips (46 miles) of a possible four return trips (92 miles). I did not need to change the chain ring this time and my filed original is working well with the new chain and cassette with no chain suck. So you definitely can eliminate chain suck and extend the life of your chain ring with some careful filing although as others have said you can also consider flipping the front chain ring over.
The top gear glitch that emerged as a separate issue really just needed a new cheap 9 steel speed cassette and replacement chain. My 10 mile return journey from work is made predominantly in top gear using the smallest cog in the cassette making it vulnerable to wear and damage. The extra power created by a crank drive bike going through the chain, cassette and chain ring must put more strain and wear on those components and off road winter conditions add to the problem.
I find my current gearing seems spot on, 38 tooth front sprocket and 11/34 rear cassette. I could try a 40 tooth front chain ring with a 12/36 rear cassette. Has anyone tried different gearing on their bikes? Does anyone have an idea how this change would effect my gearing? I think a change of one tooth on the chain ring equates to about three on the rear but I am not sure? The reason for considering this change would be to get an extra tooth on the smallest cog/highest gear in the rear cassette to help it wear a bit better but keep a high top cruising speed. I still need good low gears for steep off road sections.