It's not bad. I've done 4 hour flights from EMA-FUE and STN-RHO before with FR and it was fine. I've done EZY with slightly shorter routes from LGW-ATH and LGW-RAK and it's not really any different.
It's basically the same except you don't get a seat pocket or a reclining seat on FR (but in my experiences there's a much greater choice of food and drinks with FR and only slightly more expensive nowadays).
The only major drawback really is like you say, you have to wait a long time for the schedule seasons to be released! You could get a very good price and times with FR from EMA-RHO but it depends if you want to wait that long.
EZY will be just as cheap and a very similar flying experience but flying times may go more into the night and since you have 30 people from the East Midlands; Gatwick or Liverpool is a bit of a trek, especially if you have a 01:30 arrival at Gatwick for example.