My advice would be buy a couple of sizes but keep the receipts then you can take back the size you don’t wear.
I am six days PO today and have bought quiet a few….tesco, primark and asda ones, but went today and bought the M&S zip up sports bra for £22, well spent money !! The most comfertable one I’ve had by far, and not as pricey as the Mancom.
Good luck with ur op xx