SARREMF - I hope it won't be the cheapest bid but in order to offer more and make the package attractive (and high scoring on the review) there may be a temptation to skimp on the core issues (platform, training etc) and window dress with some other fashionable elements.
One reason for the legth of time taken is that each bidder can put in one main bid and 3 further subsidiary bids making a total of 12 to wade through and evaluate.
Sadly there isn't an MOD bid in the pot as it would make for interesting comparison and might put to bed the myth that contracting will be cheaper and better.