Like other posters, I wouldn't consider Economy Plus to be a separate class of service.

The most classes I've ever seen are the four on BA long-haul: First, Club World, World Traveller Plus, and World Traveller.

Although WT+ and WT used to be virtually the same with the exception of the seat, BA have taken pains in recent years to differentiate the WT+ product by offering amenities such as glass glasses during meal service (although the food is still the same as WT).

It's generally acknowledged that WT+ isn't worth the money on its own (and isn't worth spending miles to upgrade into); most people buy WT+ tickets to be able to upgrade into CW.