No one has ever said it is a GP 3700 cell - however, what a few people have said is that the cell is (or should be) only really rated at 3700mAh. No mention that it was made by GP. I have run some, and i think it's a good cell - seems strong. However, if runtime is your number one concern then maybe it might not be for you.
There are 2 orion 4200SHO cells - however, one of them is not legal for EFRA/BRCA use, as it is too long. So i suspect the only ones you will find for sale in Europe/UK will be the the SHO EU cell - which is within the revised sizes.