I'm new here, and I'm Swedish, so please excuse me if I missinterpret something. I also don't know what's common practice in the UK, but I'll try to not make that much of an arse of myself

Here goes...
I tend to work free-hand, but spacers have their uses. Have you tried rope/string? 3mm string for walls, 5mm string for floors, or some such, depending on customer/construction requirements.
Wet the string with a bit of water first, just enough to make it damp. You don't want yer precious, reusable string to get all lumpy with old adhesive, and the damp will prevent that. Do the first row,check the spacing with a piece of string, then "lay" the string "on top" of the first row, and "fasten" it with two or three tiles on the second row. Repeat. Remove the string and rinse it when you run out of string, or when the wall is done, or what ever feels appropriate. This method is tried and true, spaghetti is not
It works well on small surfaces, but is especially handy when working on very large surfaces, such as public baths, where deviation in the straightness of the, um, grouting, or whatever it's called in english, becomes very visible. Using plastic spacers when doing 8m*20m walls with 10cmx10cm tiles is not an attractive option, as you might need to compensate for deviations in the size of the tiles or some such. Using rope/string is also alot faster once you get the hang of it.
Cheers from land of blond babes and cheap furniture.
/sWe