A bit more info, though I note your comment about avoiding filling yourselves, it really is quite easy. I don't know what bottles you have, but we predominantly use Camping-Gas, or their bottles at least:
We got stung for over $30 to refill a 3kg C-Gas bottle in Gibraltar
, I was not a happy bunny, so decided to leave the others until Rabat in Morocco
. There we bought a local 9kg bottle (the left handed thread on it may
have matched a US one?) A spring balance, 30' of gas hose, a local regulator
and straight-through hose connections for both the local and C-Gas bottles and paid about $25 for the lot. We decanted the gas over to fill two C-Gas bottles, tied the local bottle on the stern rail and used it up when we weren't on passage
in the Canaries.
If you can get beyond the Canaries, you could buy filled 3kg Camping-Gas bottles for about (2012) $10 each at the gas station in Mindelo; some where in better condition than others, so pick out good ones.
Re: propane/butane mixtures comments and regulators for same: I believe that propane should be regulated to about 34mb and butane 29mb? Though it could be the other way around? The regulator
we got in Rabat was 30mb and marked "propane or butane." since seeing/using that, I've never much bothered what sort of regulator we're using with what sort of gas and to be honest have never noticed any difference.
One final point: Someone mentioned buying
a local bottle and when it's done, just dumping it. A fine idea, but please don't do it at sea - even the heavy steel
ones float and we once hit one off southern Spain
, no major damage, but there may have been if we'd been going faster and it scared the bejasus out of us!