14" Minilite Wheels

[AndrewB]

I have bought some 185/60/14 R888R's which I was going to use to replace my current road tyres (Uniroyal Rain Expert) on my Roadsport.  However I am now thinking of getting 4 more 14" wheels and have both sets of tyres available depending on whether I do a track day or just drive around passing the time.  

If I go for 4 more wheels my first thought is to get the same style that came with the car, minilites.  Searching through the forum it seems it is critical get the offset correct and PCD.  Is it a case that it is best to measure to be sure or is there a standard offset.  I have seen ET24 mentioned but also ET23.  Is it a big deal to use one or the other.  I guess given the way it is measured you wouldn't want to stray to far from the correct size.