The larger HMV stores with a jazz department have practically permanent sales with some choice titles.
Ace have just reissued the majority of their back catalogue in digipak format with 24 bit remastered sound (superb!). These have turned up at £5.99 in larger HMV stores.
First three I replaced with these new editions were:
Art Pepper "Winter Moon" (worth the price admission for the beautiful "Our Song". Guaranteed undie removing jazz!)
"The Tony Bennet/Bill Evans Album" (sparse and melancholy - lovely!)
Bill Evans "Waltz for Debbie" (Classic).
Verve have quite a few superbly remastered titles (they're the ones in cardboard digipaks) in HMV's current Jazz Sale. Biggest surprise for me was "What The World Needs Now - Stan Getz Plays Bacharach and David" - a gem that I've been after for ages on CD.
Another Verve I heard playing in the store and bought on impulse and haven't stopped playing was "Very Tall" By Oscar Peterson and Milt Jackson.
If you like the ultra chilled sound of Brazilian Jazz, there's always a wodge of titles by Antonio Carlos Jobim including a terrific sounding remaster of "Stoneflower" and "The Composer of Desafinado Plays..." And always knocking around dirt cheap in HMV is the Sinatra late night listening classic "Francis Albert Sinatra/Antonio Carlos Jobim", one of
the most chilled out albums ever made.
You mentioned Ella Fitzgerald; the must haves are the "Songbooks" where she takes the best of one classic American songwriter per album. Again go for the superb remasters in the cardboard digipaks with (bonus cuts) and avoid the earlier ones in standard jewel cases. Some of these are doubles and triples and can be quite expensive, although I've noticed a lot of the doubles are on Amazon UK at about £15.99 (roughly half previous price). Don't know if these are now at this price or just an Amazon offer.
Hope this is of some help.