Yes…but I don’t know where these warehouses are. I guess GW-5 is in the Czech Republic and GW-6 in Poland and GW-16 in the UK but I‘m not sure. Usually, items ordered from these warehouses arrive in Germany within 2-5 business days.
No, as far as I know there are no GB warehouses in Germany yet. But the GW-xx warehouses are at least in the European Union which is an advantage both in delivery time and customs.