2.0 Partner rear brakes nightmare

[Element]

2004, Pug partner 2.0 hdi.

Rear brakes needed new shoes and a piston changed. Shoes were the 'easy' bit. the piston is proving a nightmare job. First the union on the back od the piston was so corroded it wouldn't turn at all with a brake spanner. Had to use molegrips on the nut, the result of this was the copper brake pipe twisted and the union nut actually sheared. I cut the pipe and blocked it to stop fluid dripping everywhere.. So I bought a new brake pipe to replace the old. Part arrives and I then look at removing the old pipe. had to remove the lower shock bolt and swing the shock out the way then found the 2nd union (pipe to flexy hose) is also severely corroded and the brake pipe spanner just 'rounds' on it.. Had to remove the anchor point / support for this (with seized screw ground out with angle grinder & then screw hole drilled out ) - so I can get mole grips on the rusty union - but it's not budging at all. So I look at next option, replace flexy hose union with new... Which means undoing the 3rd union point of flext to under car brake pipe. It too is severely corroded. I am now stuck with the prospect of likely needing to create a modified under car brake pipe by a swage joint and new pipework / flexy to replace all the 3 union joints that are beyond use. Has anyone got any recommendations for this type of joint? How can I DIY swage a brake pipe in situ to make things work here? Is there another way? Advice appreciated!!!

Thinking of using something like this: https://www.ebay.co.uk/itm/353593115066 ... SwIAxff9Z4