sit down and do the maths... work out exactly how much the Zed is costing you to run then work out the same for the shed then factor in how much not running the Zed into the ground is worth to you and if the maths stack up go for it.
Mine is a weekend or trip away toy, an expensive toy but a toy all the same. my wife has a car (BMW convertible) and i have another car (BMW diesel Touring) i also have a bike which i use for 6 months of the year to get to and from worth then it sits in the garaged sorned over winter.
for me the maths doesn’t add up! the Zed is a silly expense that financially we could do without but we can afford it so we do it, you only live once and all that... recently we did some thinking about consolidating cars... selling the wife’s car and the Zed and getting something a bit silly... 4ltrs and V8... yes once we done the maths it actually worked out we would save a grand a year by doing it! the wife would have to use the diesel a bit more but it still added up. trouble is we both like the Zed... and she likes her BM so we would be selling two cars we both enjoy to buy one that we are unsure about.
sorry just realised that a lot of the above doesnt actually help you out...