Three Blades
I'm not aware of a formal plan as yet to abandon provision of FIS outside controlled airspace, but it could happen if,god forbid, there is a serious incident inside controlled airspace, and a contributory factor was determined as distraction to the controller by traffic outside.
However, NATS, who provide ATC at Solent/Southampton, have a very effective safety management system to avoid potential errors by controllers. It is possible that if traffic increases as it has over the past 18 months (Flybe already announced twelve new routes soon from SOU), this will kick in at some time and the controllers will be instructed not to provide services to traffic outside controlled airspace.
Be thankful for what the guys n' girls at Solent have done for the GA community in the past. If I'm not working, I too will be faced with the same problem of having to go around the CTA, but understand and accept the inevitable. I suspect that you do also.