Originally Posted by
Starman
You need to be aware that there is no assurance _any_ type of E+ upgrade will be offered on any given trip, regardless of price. The only way to assure E+ seating is to pay for E+ access on an annual basis. (Even that is not a _promise_ of E+ seating, but as long as you book in advance, it would be very rare for E+ not to be open).
If you're planning on a two-way trip to LHR, and want E+, you may want to seriously consider buying E+ access for 1 year, or else begging any 1K friends of yours to gift you a 3P or 2P.