NutLoose,
The SDSR didn't deem that they weren't needed at all. It deemed that the capability provided by the R1 would be replaced by 3 RC-135 Rivet Joints, and that while they were being converted in the US that 51 Sqn crews would fly on USAF RC-135s out of Mildenhall.
I guess that this extension is only until those crews are deemed CR?
Now, which bunch of clowns thought that we could get by with such a capability gap, that's a different matter, but I guess those folk wear blue...