Don't worry - GB service is equal to and in many cases better than BA Mainline.

But Be aware that European Business Class is not the same as US Domestic F in terms of seating - it will be 2x3 layout with about 34in pitch (some GB planes have 33in in Club).

However the food and drink shoul be better than you would get on many Domestic F flights in the USA - champagne from a bottle and a hot meal.