I believe tethering on orange is restricted to the orengeinternet APN which is again restricted to contract customers. PAYG users use the orangewap APN. Roaming BIS prices are set by RIM in the uk not the carriers. I believe it currently to be round a fiver per 24 hours for contract customers. Roaming charges on wap/tcp or any mapping software would bite you HARD while roaming on PAYG. Get a 30 day contract for your trip.