Hi Thrifty, Kays have quite a few box valance sheets - call 01 811 2222 to order a catalogue or shop online at [broken link removed]. I've bought a few in the past and the quality's not bad and they're delivered to your door. If they don't suit, keep the original packaging and send them back.
Hope this helps with the sheets - I have some blackout blinds but had to have them made to measure and they were around E80 per window. Alternatively you could get some blackout material, hem it and run a curtain wire thru the top of it yourself. It doesn't look as good as a blind, but would do the job if you're on a budget.