Richers have the Shure SE215 iem for £209 .
They come with a selection of different types and sizes of ear bud cushions . They have great sound quality , excellent isolation with no leakage so you won’t need sound cancellation and you can turn on an external mic to let you hear the outside world .
I have the 5s for travelling and serious listening but use the 2s for gaming and late night movies.
6 year warranty
If you want cheaper Richers have some offers on normally .
I generally won’t touch anything but Shure for iems , open backed will be Sennhieser HD series , closed back would be Beyer Dynamic .
The Sennhieser HD open backed are probably the most comfirtable headphones out there as well as the best sounding . But they are open backed so leak and don’t give any isolation.
The Beyer Dynamic DT220 are a good alternative if you require closed back . I use these a lot in studios and they are very robust , comfortable for an hour or so and have decent isolation and good frequency response . BD also sell pretty much every spare part so its easy to repair them if required.