Britain no longer has an Army: technically speaking, we have only a defence force, since it has a manpower capacity below 100,000. Our island, trading nation also has next to no Navy left at all. And the Neocon Ascendancy with which we are still afflicted (as are several other countries, but no longer the lucky old United States) continues to lobby for the RAF to be abolished entirely.
If their Commanding Officers really want "Our Boys" to be treated as national heroes, then they will order a full, immediate and unconditional withdrawal both from Afghanistan and from Iraq. They could be home before Tony Blair had even noticed, and they really would be cheered through the streets on their return. There is no identifiable "job" to "finish" in either of those countries, and our presence in the latter, at least, has always been illegal; so if Blair or anyone didn't like this withdrawal, then they'd just have to lump it.
After all, who has the guns and the tanks anyway? And who, moreover, would have the moral and legal high ground, and the popular support?