Hi Chris

We used to live in Sutton Coldfield until about two years or so ago and it might be worth trying the company
I used for a pistol lens about twelve months before we moved. One of our club members had put his business card on the club notice board and several members had used him. The company is Alecto Optical Solutions, Unit E09 Hastingwood Industrial Park, Wood Lane ,Erdington.B24 9QR. 0121 386 6614. The chap I dealt with was Neil Tredell who I think is the boss man. I did have a bit of a job locating him as the estate is a rabbit warren of small businesses but it was worth it when I found him. He was happy for me to take a pistol in and try various lens in his frames until I was happy I had what I wanted and he then made a 42mm lens for my frames. Price more than reasonable as I recall. Worth a phone call anyway.
Hope this helps
Regards