Just got back from an hour at the pub during which Poppy was excellently behaved. We went in the trailer and after she'd eaten all the peanut butter from her Kong she started whining again. She was excellent in the pub, chewing her bully stick happily, and then started singing on the way home in the trailer again (we stopped for a 5 minute walk on the way back).
I think she may just be a bit noisy in the trailer until she learns it doesn't make any difference. I am sure it's because she wants to be outside running rather than confined, as it's the same noise she makes when we shut her in the kitchen. When her attention is on the Kong she doesn't mind at all.
I'm trying to decide whether to also persevere with the bike basket (which is tricky to use with kongs/chews as she will probably post them out of the bars) or just keep with the trailer.