Assuming that the router is acting as a DHCP server are there any fixed IP addresses set by any of the laptops or the router?
Maybe it is working until a DHCP lease expires?
Ex <n>ildram , been to SKY MAX - 15,225 Download
BE Unlimited - 21,000 Download 1,200 Upload,
Moved house, now BE Unlimited 6,500 Down, 1Mb/s up - gutted!
FTTC Cab installation commenced 12th April - expect full 80 / 20 - bye bye BE, hello BT Infinity soon!