Sandie,
I would strongly recommend the RAF do not buy "off the shelf this time", well, at least not yet. Many of the reasons we didn't buy "vanilla F" last time are still valid - these include heavy optimisation to US Army requirements/TTPs/SOPs (quite understandably) which would place some very unwelcome limits on UK capability (just as a few examples, the F had no FLIR, no M134 capability, no means for the rear crew to assist with on-board mission replanning/mission management nor did it have a rotor brake which makes Ship Ops and mountain operations "interesting").
AFAIK the CH-47F Block II configuration has yet to be frozen, and that would be the aircraft we would need to go for to leverage the through-life savings. We don't, therefore, know if the upgrades to the Block II actually assuage the concerns the UK had back in 2010 nor the requirements we have now or anticipate for the mid 2020s. If the Block II either meets, or is adaptable to, UK requirements then by all means let's jump on the programme and exploit those savings. As for -718, she's probably a lot more "original" than many data-plate rebuilt Spitfires......I'm however a little torn as to whether we preserve her as a Mk4/6 or put a Mk2 cockpit back in her....I think all her DFCs were in "steam mode"....