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Yep, Airfix owned Heller at one time, before the take-over by Hornby. The Airfx kit is the Heller kit, and I think still around under the Heller label, as they are now back producing kits.
Heller did both the L-749 Connie and the 'Super Connie', and both are in stock (at the moment!) at King Kit in the UK. Around £15 for the L-749 (pre owned) and £30 for the 'Super Connie', the latter I believe being new. Note that all 'Pre owned' kits are complete, m any being ex-stock from closed shops, or private collections.