One of the British musicians (sorry, I can't remember which one) told me that the Americans went mad for drink over here because they couldn't get it back home due to Prohibition. All three Americans in the original Elizalde band were regular imbibers, but particularly Chelsea Quealey and Adrian Rollini (amongst the later additions, Max Farley and Fud Livingston were also heavy drinkers). Norman Payne recalled that Quealey carried a hip flask, like Bix: "Bix has this habit of carrying a flask in his pocket and Chelsea followed suit. He did exactly what Bix would have done". Harry Hayes said that the only way that one could tell that Rollini had been drinking (apart from his breath!) was that he would play with his eyes closed!
When Adrian Rollini returned to the States in February 1929 to secure the services of additional musicians for Elizalde's enlarged band at the Savoy Hotel, he tried in vein to hire Bix and also Bing Crosby. But Bix was still too ill after his breakdown and Bing wasn't interested (he was already eyeing Hollywood). Norman Payne, an avowed Bix disciple of course, remembered the near-miss with his mentor: "Adrian told me about trying to get Bix and I thought 'Oh Christ, that would have been lovely!'"
Interestingly, Norman said that Rollini never went jamming after hours, as most of the "drinking musicians" would have: "He probably didn't want to lug that big bass sax around". But Norman remembered Chelsea Quealey jamming with him at the famous 43 Club: "We always went to the 43 Club and we always went to Lyon's Corner House. That's where Chelsea would eat fried eggs with fried onion rings on top!"
The only visiting American jazz/dance band musician of that era I know of who wasn't a drinker was Sylvester Ahola. He said he was too busy to go out jamming, but booze was surely another factor - I don't think there could have been many teetotal musicians jamming the night away in smoky London dives! If you didn't drink, it would have been difficult to fit in with this booze-oriented after-hours scene.