I'd suggest that the Surrey / Sussex collaboration is really no change, or an improvement, to the situation that existed before April Fool's Day - these dates are always so appropriate, aren't they!
Given that Hampshire had already retired their fixed-wing, Surrey had been covering their neck-of-the-woods anyway. Getting into bed with Sussex only means that there's a bit of mutual aid when one unit is stretched with a job at the end of its leash, or down for maintenance (this has been working in East Anglia for years). For slow-time jobs, this isn't really a problem, as an extra 10-15 mins transit will unlikely affect the price of fish, although it could cause problems if they need to haul-ar*e back to their own patch. Any task, requiring more rapid response, however, will be invalid if either machine has a long transit, collaboration or not.
As with this whole plan, the singular failure is in the understanding of the importance of transit time for different jobs. Reaction time is critical to effective aerial policing of many tasks - the really sad thing is that too many believe (from Chief Constables (having been sold "savings" by NPAS) to Control Room Inspectors) that getting an aircraft overhead, no matter that the horse bolted some while previously, is the only thing that matters. When it comes to the crunch, they will be able to say that they "deployed all resources available", no matter that the longer (than pre-NPAS) deployment time completely neutered the effectiveness of the airborne resource.
There's so much time spent covering backsides, that there's often little left to get on with the job!