Any decent plumbing supplies will stock them. Sheds on the other hand...
You can get a repair compression joint which is longer than a normal compression joint. One end is as normal - pipe fits up to a constriction in the joint body and is gripped by the nut and olive. Other end is a long tube which can be slid back up a pipe to give clearance, but still can grip when the nut and olive are tightened. AFAIK you cut a bigger gap in the pipe, slide the repair joint up one pipe, align the ends and slide the joint back down, tighten the standard end then tighten the slidy end. Never used one but I bought one the other week at a B&Q warehouse place 'just in case'.
In the case of replacing a compression joint, I guess you undo the nuts and slide them back, then cut the pipe near to the olive so it all falls apart :-) I guess you should really trim both ends just behind the olive to fit the new olives, but you may be able to re-use one nut and olive if the threads are compatible - your choice.
HTH Dave R
BES do slip fittings.
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