I couldn't really find anything on this as most information is for US carriers.
If I buy a Pixel on a 2-year contract in the UK, it's often cheaper than buying it from Google directly - AND you get 2 years of data and phone service "for free".
Are UK carriers doing the "OEM locking"/"bootloader locking"? Or are they just doing "SIM locking" and if so, would that be a problem for installing GOS? I don't mind being locked to one carrier for the duration of the contract, but obviously I don't want to end up with a Pixel that can't install GrapheneOS.