Just wondering what I should expect to pay for a good blade to cut porcelain tiles? It'll be a 4.5" blade to fit my grinder. The guy in one of the local tile shops showed me a £30 blade he "sells to all the professional tilers." I've seen a diamond edged blade in toolstation for £3. But I know you get what you pay for - there must be an upper limit where there's no value add it's just extra cost. Can someone recommend a good blade that will be available in a local retailer - screwfix / toolstation etc.? (my tiles are 59x59 porcelain and from memory either 9mm or 12mm thick) Also they tend to be thin blades are they typically mounted with a backing plate?