Highly recommend getting a realistic valution of a site like pinballinfo.com, and if the machine is not in pristine well maintained condition (which I assume because you are not a collector with many machines and a workshop) I highly recommend selling to someone from a forum for the lower ballpark on a no-refunds condition.
I have restored/repaired 30-ish pinball machines with my FIL over the last three years. They always have issues than you expect and can be flakey after transport. You don’t want to sell for max price and get a complaint from a buyer that stuff doesnt work anymore. Its not worth the headache…
I am unfamiliar with UK prices, they tend to be lower than NL, but I think a stock TZ (no expensive mods) would be between £4500-£6500 depending on condition.
Good luck