I've moved on to looking at modifications to the firebox and boiler.
Firstly the firebox, which does have differences compared to the casting from 20 years ago ! However, I decided that the cast mounting plate for the safety valves needed to go, to be replaced with brass sheet of the correct shape:
You can see the differences here, with the brass replacement being fashioned on that from a view above 48305's boiler/firebox in the Wild Swan book on the 8F's.
The replacement part in position awaiting soldering, after which I'll drill into the firebox and fit some 0.5mm rivets.
Whilst at the East Anglian Model Railway Show I purchased this little lot. Thanks JohnK !
Ian