My experience is that EG and G&G sizing, at least for the TG73 last, are very different.
I have one pair of EG in 888 and one pair of G&G in TG73. My G&G TG73 (the pair I first got) is a UK size 7D and it pinches my toes something terrible. I find the toe box far too small and can't wear them comfortably for more than a few hours. The problem is all in the toe box because elsewhere the fit is either OK or loose. My EG 888 is a UK size 6.5D and if anything it's slightly too big. I still have some room in the toe box so I'm considering sizing down to a 6.5C or maybe a 6D in order to get a snugger fit at the heel to get rid of some heel slip.
I'm told by EG that I don't have duck feet at all, in fact that my toes taper in to my big toe very nicely on both feet, so it doesn't seem to be down to me having totally weird feet. My experience is that the toe box on a TG73 really is narrow.
Another point on G&G sizing is that, if you find the Deco last too pointy for your tastes then, in addition to the fit issues that I already mentioned, be very cautious about sizing a TG73 down to a narrower fitting for aesthetic reasons. Going to a narrower width accentuates the standard level of pointiness of the TG73 last and mine ended up looking rather too much like the Deco last for my liking.
I have the same problem here Julian. I fit perfectly well on EG888 7E but had such terrible experience with fitting on TG73. Based on conventional advice, I tried on TG73 7E but the shoe is so tight I can't even walk with it, so then I took a half width up to 7F and it fits perfectly - except the toes, the toe box pinches so badly I hardly wear them now, I tried half size up to 7.5E but the shoe is too lengthy.
All in all, the fitting problems I have with GG are almost to the point of giving up (while I fit so perfectly on EG most standard E last). Maybe I should try MH71 some point in time