I've called the trackday organisers and I've been told that there are no drive by noise tests at Mallory Park apparently there is just the static test if you are considered too loud when driving round. Might take the stock exhaust in the boot just in case
Don't take the stock exhaust in the boot, just take the bungs and a rubber mallet, then you can fit the bungs in 5 mins to quieten it down.
I found the best tool by far was a rolling pin