Hello shottyscotty (like the name)
have a look here mate http://www.gamebore.com/index.asp
I'm not sure about your gun being suitable for steel shot, have you asked at your gun dealer (good one in Dingwall) I've recently gone through the same scenario, I have a Miroku MK38 3/4 and full fixed chokes, everyone tells me no more than half choke. I first tried steel shot at The Highland and Deephaven Clay Club, they performed very well and clays just turned to dust but I did notice an increase of recoil.
I hope you don't mind me asking this but where on The Black Isle are you, love that