Where can I buy the foil trays (30 x 20 x 5 cm) as recommended in your latest book 'Kitchen'?
The foil pans used are made by Weber and are large BBQ drip pans. They can be bought in some supermarkets and garden centres. They are also available my mail order from the sites below. Bacofoil also now do a foil pan in this size which is available in Sainsbury's and can be found in the household section with foil, clingfilm and freezer bags.
For the US you can buy buy the 13 x 9 inch large Weber pans in some hardware stores and DIY depots. Yo can also buy on-line from Weber. You can also use Handi-Foil 13 x 9 inch utility pans which can be found in many supermarkets and grocery stores. We would suggest using the deeper utility pan rather than the shallower cake pans.