If you change to the LX flight you should be able to interline if your connection in London is under 24 hours.
If that fits your situation and the flight isn't much more expensive than the EasyJet flight then I'd go for it since you'll get out of the excess weight charges that way. If the bags are interlined then you are supposed to get the weight limit of the original flight which will be 40lbs x2 or 50lbs x2 depnding on your airline to the UK.