the cheapest way to do it seems to be via GolfGearDirect and TopCashback, which gives 9.45% back on the purchase (£15 on personalised balls). Can sign up for topcashback here: https://www.topcashback.co.uk/- then find and click through to GolfGearDirect via their interface.
I have seen this offer over the years for prov1, tp5, chromesoft etc. Looking to game the Bridgestone tour bx this year, but can’t say I have ever seen similar offer on Bridgestone (anybody know if a similar offer happens for the Bridgestones?) if not might have to bite the bullet and just go for the prov’s