Raleigh padded bike bag with wheel inserts £15
Was £30 new and that was quite a good price. Has been used a grand total of once to transport my bike in a van. It's located in Cardiff and doesn't fold up that well, but I think Hermes can deliver for well less than a tenner.
Also Carradice Carradry panniers -free. They've had a tough life at the hands of my other half, but they have some life in them still, the hardware is basically bombproof so they'll probably last for ages really. Again, pickup in Cardiff or post at cost.