I recently got a QWER tester via a mass drop. They are apparently located in the UK, which should make it good for you. It included 6 switches: blue, green, white, red, black, and brown. Apparently they're planning an 8 key version which include a clear switch and something else.
It's really easy to pop switches in and out of the board for testing. I bought a few clears and blues to experiment on. (Not sure where you would source those in the UK.) The QWER plate makes a great platform to do it.