It is actually a really nice flight I have been using a fair bit in the past, the SUN AIR Service in my opinion is far better than the normal BA shorthaul economy service, very attentive and friendly. And if you are a bit of a geek like me, you will enjoy the flight.
Sometime soon during the summer the SUN AIR (Mhs) flights will be replaced by the Eastern Airways SAAB 2000 on this route, so the only dornier prop out of LCY will then go to BLL.
Cabin crew are very friendly and chatty (like most of BA Crew may I add) and it's a nice little set up. Enjoy and let me know whether you liked it or not if you go on it.