I have a Pantone Formula Guide; Can I use this for matching fabric colours?

Yes, you can but fabric suppliers and mills will find it much more difficult to produce a good colour match to this especially to the coated version because of the shiny appearance of the paper. The Fashion, Home & Interiors range of colours have been specifically developed because they are achievable on fabric whereas the Formula Guide coated is for Graphic Designers to use for logo colours and printing on clear film and white paper and so many of the colours are too saturated (bright) to be achievable on fabric. We advise that you select colours from the Fashion, Home & Interiors books and then send your suppliers individual SMART swatches for them to use as a colour standard.
The only exception to this would be printing of licensed artwork onto fabric as most licences artwork colours are specified using the Formula Guide Coated numbers.