wsmempson - you sound as if you aren't too familiar with Sleap. There should be NO difficulty with radio discipline as Sleap is within the Shawbury CMATZ and Shawbury ATCOs prefer everyone flying to and from Sleap to talk to them - plenty of discipline available there and they insist VERY politely (and with seemingly infinite patience on some occasions) on correct readbacks, terminology etc whilst remaining pleasant and helpful. I don't fly from Sleap but have flown through Shawbury CMATZ on numerous occasions. Shawbury is a very busy place which handles a lot of civil traffic as well as military (both on separate frequencies) and has both the Military Helicopter School and ATCO School.
Slow Progress if you fly midweek you will certainly get plenty of practice in talking to MATZ ATCOs and won't have any of the irrational fears some people seem to have about requesting ,then flying,MATZ transits etc.