David, I don't know if you have an alko or BPW chssis. I have BPW and it has the holes already fitted for an alko carrier.
I have a carrier fitted which is similar to one currently on ebay item 4576757540, which is basicaly a single tube with a cross section for the wheel to sit on.
The one on ebay is as good as any of these types. It is important to take it apart twice a year and grease the section that slots into the largeer box section. If you don't it may be a hack saw job to get it apart. It is important with the cross section to keep that greased as you need to pull it towards the chssis so that when it is lowered it will clear it whilst being pulled out. I am relatively fit for my age but wouldn't underestimate the strength required to drop it or lift it back into position especially if the puncture was on the side which is lowered - that applies to all of them, including the alko.
Make sure that if you have 14inch wide profile tyres that it is not too large or you may find it hitting the floor before it is in position, alko do different sizes. Check there are no obstructions i.e. gas pipes, heating ducts etc.