Problem parting air con pipe connections

One of my lower air con pipes on my 1998 XKR was damaged by rubbing perhaps for years against other metalwork (leaking the air con gas through a small hole that had appeared). I have purchased the required new air con pipe section but I just cannot get apart the aluminium connections. It appears that the aluminium connection ports (after 21 years) have corroded together. It is obviously in a very tight space to get your hands in with any tools, and with all the pipework down there being aluminium and delicate connections to the air con radiator, etc I am concerned that too much force will brake other pipes or connections (and a very expensive job!!). I’ve applied penetrating oils for several days. I’ve got one threaded “peg” out from one side of the connection port but the other side “peg” will not move (although I’ve unscrewed the top retaining nuts OK).

Any suggestions or advice please in freeing these aluminium connection ports in situ under the car?