Mike,
Best to get this issue checked out by someone that knows there way round a Zed, a simple road test will determine whether there is in fact an issue or whether you may just have to change your driving style slightly to overcome the issue.
A fluid change for the proper OEM fluid and 60ml of DC Moly additive can also work wonders and make the gearchange so much slicker.
I have both the above in stock mate.
If in fact there is an internal issue, then a preowned low mileage transmission would be the way forward and you can expect to pay circa £400.00.
I note that you have just purchased the car, perhaps you may have a warranty or perhaps a financial goodwill gesture from the seller may be an option to explore.
Drop me pm if I can help you further or if you have any further questions.
Alex.