Expedia.co.uk will give you Nectar points. It's not much but maybe translates to a few pounds off groceries after a long flight.
The UK is nearer to a wide variety of travel destinations than the US is. You can make your American Facebook friends totally jealous of your adventurous life with very little investment. In the States, if you drive or ride on a train for 1000 miles, you can maybe get to Canada or Mexico or maybe just to another state. If you do that from England, you can get to Vienna or Barcelona.
Ryanair has amazing prices if you book ahead and travel light.
SailRail is a lot of bother but a pretty good deal between the UK and Ireland. I waited too long to get a good price on a flight from Dublin to my city in England, so I ended up booking SailRail with Irish Ferries instead and made the trip yesterday. It took a lot of extra time, but the scenery was interesting. This was to connect me with cheaper flights to and from the US out of Dublin.