Hope I have done this ok.
DVD crave as part of their blowout now have the mission impossible trilogy for $24.95 AUS which works out at £10.60 before delivery. So it is about £15.50 including delivery so should be under the magic £18.
I have ordered and I hope others find it useful.
Couldnt find a merchant for dvdcrave or create one so sorry if it appears in the wrong one.