I suspect the buying plenty part is one of the OP's reasons for wanting a tuner.
In the UK rifle shooters cannot buy unlimited quantities of ammunition. The maximum amount that can be purchased or stored* is limited. The OP has mentioned 1000 rounds, which is not uncommon for club and sporting shooters. One can ask for a higher allowance, and Home Office guidance (our Dept of the Interior that the Police answer to) is that competitive target shooters should routinely be allowed more, say 5k. But you have to show good reason, such as shooting on a county team. Wanting to buy in bulk is not enough.
Bear in mind Police Firearms Licensing Offices aren't filled with shooters, and staff probably don't expect a sporting shooter to want to batch test, if they even understand that nuance. Normally a license for vermin shooting covers zeroing, but not regular target shooting, hence ammo allowances aren't especially large. The police would expect one to join a club for regular target shooting, and most clubs sell ammo membership isn't an automatic pass to a higher holding.
*For many years these were separate; the allowance to hold was slightly higher, so one didn't have to run out completely before restocking. However this changed a few years ago, and there is now on