I can't be sure whether the Acer's prefer ericaceous soil, but I have a very healthy acer in my garden, which is alkaline, and it is very healthy. I have also grown them in large pots, but find that they do better in the garden.

If you're talking about a palmatum variety of Acer, they don't like chalky, alkaline soils, but will grow perfectly well in neutral as well as acid soils, so ordinary multi purpose compost will be adequate, as its pretty neutral, or even John Innes No. 2, which is loam based, or the two mixed together. If you already have ericaceous compost, then use that, but don't buy it specially, its not necessary.

thank you both for the info