For flights a bit further from home a few things I keep to hand;
list of listening squawk codes
LARS frequency / coverage chart -
http://www.nats-uk.ead-it.com/aip/cu...6_1_6_3_en.pdf
FIS frequency / sectors chart -
http://www.nats-uk.ead-it.com/aip/cu...6_1_6_3_en.pdf