Looks like it was in 2007 watch dog did the article on spray foam.One of the big problems with the spray foam was if it's done to roofs with no felt i.e. direct to the tiles or where the felt is damaged. Tiles are supposed to slide over each other as the roof expands and contracts. But the foam locks them altogether cracking the tiles on the nails as the timber expands. I think there was a "watch dog " program or similar on it.
Can only find this link
Watchdog - roof spray-on foam
At last! This evening's edition of Watchdog included an item that came down heavily against the use of spray-on foam for the underside of roofs. Perhaps this will help put an end to the use of foam in this totally inappropriate way.
www.periodproperty.co.uk