IB J is comparable to Club Europe. Maybe better food and wine though (depends on the route, rather ironically the IB regional jet flights have better catering than mainline). The transfer to LGW is notorious for being of unpredictable duration (the buses can get stuck in traffic for hours on some days, apparently, though most of the time it is no problem). Baggage cannot be through-checked if doing this transfer (you must lug it from LHR to LGW yourself).