Hi Iain,
I bought my kit from Modellino - see the recommended vendors thread for Peter's contact details.
The Zimm is milliput, each individual mark was made with a flat screw driver - it was an early effort so its not as good as I'd like (I didn't keep the milliput wet enough until I came to make the marks

)
My Tiger 221 build has benefited from that experience...
If you can get a friend to turn down a gun barrel for you I'm more than happy to supply the dimensions, failing that you can try asking Peter to just supply the parts you are intested in...

I am going to try to get a set of early T34 track guards from his T34/76 upgrade kit - I need them for an early SU-122 build... wish me luck
Cheer's
Mart