Before you purchase anything, think about how you are going to use your simulator:
Do talk to your neighbouring towers and your District or Branch to see what use they might like to make of the system and whether you can collaborate on funding or installation.
If you just need an alternative form of sound control, you can this relatively cheaply, but you will be missing out of many of the benefits of a simulation. If your bells are difficult to access, to silence, why not consider one or more dumb bells in the clockroom?
If you are going to use it for one-on-one practice, you will need a screen, but it does not need to be a large one. To make the most of this a triple action foot-switch is recommended.
You can have more than one workstation so that several ringers can practice different things at the same time. You wil need several computers and several sets of headphones. Some sensor systems are unable to cope with multiple workstations so future plans may influence your choice of system.
If you plan to have multiple workstations do give some thought to where the computers will be placed, and to cable management. Cost in for additional power sockets to be professionally installed, if needed.
Don't try to do things on a shoe-string. Be bold. Many ringing societies will contribute to improvements in teaching facilities from their bell restoration or training funds and certainly allow for this in any bell restoration project. There are also many local charities which will contribute to imaginative projects, especially when they involve people gaining access to heritage and work with young people.
Ringing simulator with multiple workstations at Mancroft Ringing Discovery Centre