Thanks dude. Here's a cost breakdown I did for another forum:

Return ferry ticket Hirtshals Denmark to Seydisfjordur Iceland, couchette class (literally sleeping in the bilge ), including 1 meal daily: £393
Eurotunnel return fare: £72
Fuel, food, , camping, sundries etc: £1370

Last time I properly checked, my bike does 49 mpg at low non-motorway speeds. At motorway speeds however it has dipped to around 35 in the past. I did 3083 miles, the vast majority of which was motorway. UK and Iceland average petrol price is circa 128p per litre for the period I visited. So the total price of fuel I burned at 49 mpg is: £366. This rises to £448 at 40 mpg and £512 at 35 mpg. So who knows...

I did blow a lot of money on board the ship, buying many many s at the bar over a total of 6 nights at £5 each, partly because I didn't bother checking the Danish Kroner rates etc - but mainly (and quite rightly) because of the "f**k it - I'm having the best holiday ever!" attitude which I don't have to justify to anyone! I also partook in one-off events like going in the blue lagoon (£20) and splurging on Icelandic delicacies in restaurants a couple of times (not cheap at all!), and buying souvenirs.

Camping at campsites is something like £6 a night. For that you get toilets, drinking water, hot showers, and even laundry facilities sometimes. You always get someone come along either in the evening or the morning who takes the money. They have ID and a card machine and always give you a receipt. If you're organised (not like me) you can collect all receipts and fill out a lengthy form back on the ship and get tax back. Sometimes nobody comes in which case it's all free.

Petrol stations are all automated in Iceland, meaning you use your bank card + PIN not unlike using a cash machine. I'm pretty sure my bank stung me good for that. Towards the end of my trip I discovered that you can buy pre-pay cards for cash - would have saved on bank fees on each fill-up.

So all in all not cheap. But 1000 times more enjoyable and rewarding than an easyjet holiday somewhere!