Hi and welcome to the forums, I'm sure you would love the zed and the rear wheel drive aspect of it, having once owned an astra gsi this is by far a much better drivers car, (just be careful in the wet)
You should be able to get 2 golf bags in the back and believe or not there is even a picture in the boot showing you how, I've never done it though
As for MPG, I also use nothing but V power and normally run an average of 27 mpg doing a mix or motorway and town driving, it only ever drops as low as 18 or so when I really thrash the hell out of it which is rare, but as others say, this isn't a bluemotion and likes a good drink
as for road tax, pre April 06 is about the £230 mark I think, post April 06 which I have cost me £405 last year which is a kick in the teeth
As for servicing, depending on if you buy a car still in warranty or not but there are a lot of independents that offer services much cheap than the main stealers, all depends on where you live but a P3 service ( the big one ) can be around £250 - £300 mark, using the search button above will also give you loads of advise, there is so much here
Good luck, get a Zed, you won't regret it
(excuse the spelling, typing this on an iPhone and can't be bothered to change it)