So if someone purchase 2 bats at 150 & 250 then the 25% discount applies to the lesser value bat. Its common here in North America where you can buy one item to qualify for a discount on another item that is either the same value or lower than the first, usually it is buy one and get one half off (50%) which works out to be a 25% discount of the total amount spent on 2 items...on a flip side customer could pay 400 (250+150) and Not use half off the 2nd item and which then qualifies them for 50% off on anything that is 400 or less for a future purchase...
second part of the suggestion i am not sure i understand completely..but my guess is sell vouchers for 30-40 that have value for 50 and could be redeemable at anytime in future...we get these locally too where a customer could buy vouchers worth $200 but paid $150 for them (5 x $30) and use them in future when ever they wish to buy gear upto $200 at your store. There is no cash value for these i.e. if I purchased gear worth 175 and then i can't get 25 back even though the voucher value is 200, 25 cannot be saved for future use (one use only) etc...atleast thats what the terms are here...you can combine multiple vouchers but not use half value now and half later...hope it helps..
Also these vouchers usually do not cover tax or shipping costs, so if gear was 110GBP and VAT was 10GBP + 5GBP postage and customers vouchers were woth 125 then the customer would still have to pay VAT and shipping costs total of 15GBP (they would not retain the 15GBP from the voucher for future)