Keep it up - Your title was ELT requirements and I suspect that is also your question. On the UK register, I believe the answer depends on whether you are operating public transport (406 ELT required)or private (nil requirements). Also, your beacon was fitted before COSPAS/SARSAT stopped monitoring them in Feb 2009.
Don't be too upset though. You have to think of rescue beacons as doing two jobs: alerting people of your distress and helping to locate you. 121.5/243 was always a very poor method of alerting even before it ceased to be monitored by COSPAS/SARSAT but is still a very usefull method of locating you if you are in trouble. All UK rescue aircraft can home to these frequencies.
If you are UK registered, non public transport and you normally have comms with somebody when you fly (in other words, some method of alerting people to your problem) then a 121.5/243 beacon is more than you are required to have and probably as much as you need.