Thanks for all this. OK - I have taken your advice & booked a flight to Dublin in the morning. Everyone I know think I must be crazy to do this - but hell it seems to work!!

The flight to Dublin was only around 20 GBP anyhow.

Coming back, I still think I must be able to spin them a story to get my bag. For example, I want to meet a friend in London and pass him some souvenirs blah, blah!!

It's not an overnight stay, but I must be allowed to take my bags if I am there for 7 1/2 hours? Never done this before....

Hope the bags don't get delayed, and routed straight to Dublin! Otherwise you might have to go and get them from there!

Plus, make sure you have enough time between flights in Dublin - several hours at minimum - in case your first flight is delayed (in which case, you would miss your dublin-London flight, and thus your London - NY!) as they are not on the same ticket, thus no obligation to accommodate you on a later flight. Allow time to collect and recheck bags too, although I would probably just consider carry on - you will likely have to pay for checked bags on London - Dublin anyway (airline dependent), and it is a lot easier coming back without checked bags. Or if you really need stuff, you could use a luggage courier?

Reasonable story to get your bags back - you will be overweight on hand luggage once you have purchased your duty free items, thus need to check them?