Formatt/Hitech filters for B&W?

[Peter B]

I've done a Forum search and it seems that most of the posts on Formatt/Hitech deal with their grad filters and possible colour casts. I'm looking to find if anyone has experience of their coloured filters for b&w as I'm thinking of buying a set? The Hitech 100mm CR39 resin set of Yellow, Yellow/Green, Orange and Red comes in at about £60 inc vat, which is about double the price of the equivalent Lee polyester set. The CR39 should be more robust than the polyester set, but I'd be grateful for any user impressions. Oh, and is it only at workshops that we can get bargain Hitech filters?

Edit: should have mentioned that I already have a Lee holder and adaptors.