There are probably dozens of capable helicopters in storage in Arizona that could be put back into service, however there are not the (UK) qualified crews, nor the defensive toys that they need in sandy places. To suggest WG30 or Wessex is I hope a tonque in cheek comment.
An option may be to employ aircraft without defensive toys on UK training and routine tasking to enable fully equiped aircraft to deploy en-masse. Though mixed standard fleets is not what UK mil plc normally approve of.
Bottom line; we now pay the price for a lack of investment in the last 20 years. Even Chinooks date back to about 1982, Pumas 1971 and Sea Queen about the same. The Merlin fleet should be the be all and end all these days supported by upgraded Chinook. The HCII Puma is well overdue is place in the RAF Museum, and should have been replaced years ago.
Quick fix would be to contract the likes of Bristow & British Intl on contract for rear echelon bus runs, or make use of short rough landing strips for the likes of G222/Spartan fixed wing.