... and in And Here The Wheel in a system which
“registered explored on the maps, but was sufficiently far from civilisation to be of little interest; a common-as-hydrogen red dwarf star, an asteroid field behind them and a blue-green gas giant hovering in space ahead. And apparently orbiting the gas giant was Gunn’s Circle base.” And that rotated to produce imperial standard gravity so likely in Imp space.
Unfortunately this is not a helpful description anymore. The book's final edit came before the galaxy was rebooted at some stage. This has resulted in systems changing contents, as can be seen if you try and follow anyone's system descriptions in the books. In addition the game graphics changed too, so there are now no blue-green gas-giants at all. I've spent an awful lot of time looking for that system and looking at every system I went to for months to see if there were any blue green gas giants. No cigar. I know others have expended considerable effort on that description too, to no avail.