Jochen Merz Software mainly deals with QL related Software, just like the name implies. For hardware, best contact some of the QL dealers in the UK - like QBranch or TF Services.
Spare parts for the QL, e.g. ZX8301, ZX8302, are still available through J-M-S. If you wish to inquire about the price, send an email to SMSQ@j-m-s.com and let us know how many you need.