Two things to consider for your trip:

1) The UK charges fairly high taxes for landing in the UK, particularly for business and first class. You would be responsible for the taxes (at least for business and first, never redeemed an award coach seat to the UK).
2) CLT-LGW is in the 733 which doesn't have the new seating, but rather more like a recliner. If seating is important to you, consider CLT-PHL-LHR on US as it has the new suites product, which is quite possibly the only time in the past decade or two that US has done something that could be considered innovative and truly good.