Holiday oxygen in France

This is an update to my original question, which I have now managed to resolve, so I'm posting the solution here. I have been unable to work out how to delete a post and replace it with a new one, so ignore the first response (no disrespect to Val). This is pretty comprehensive.

The following will only change in the event of a no-deal Brexit, but even then it should still be possible to arrange it (it just won't be reimbursable as part of reciprocal healthcare arrangements).

First of all, AVOID Oxygen Worldwide. They were suggested to me by the British Lung Foundation, they quoted €630 for single cylinder, not reimbursable under any circumstances.

I found the name of SOS Oxygène via the French CH support group. I'm not sure of their status (for profit, not-for-profit), but they are excellent, and very reasonably priced (and the costs may be reimbusable; update to follow). They have branches all over France. Just Google them (or use link below), find the branch that covers the region you will be staying and email them with your travel details (date, address in France, address in UK, contact numbers). It helps if you speak/write French, or can get a Francophone person to do this on you behalf, but there is likely to be someone there who can speak English. They will require a copy of your prescription (in my case, they accepted a scan of a letter from my GP, stating that I had been diagnosed with CH, and had been prescribed oxygen at a flow-rate of 15 l/min, etc.). They delivered the day after I arrived, 8.30am. The cost was €115 for the delivery (including collection at the end), plus €16 rental per week for the oxygen, regardless of quantity, making the total €147 for 2 weeks, payable in cash on delivery. This is potentially 80% reimbursable, but I have yet to find out. Even if not, it's considerably cheaper than alternatives.

The one tricky thing was that they required a deposit of €500 in the form of a cheque drawn on a French bank account, which they said would not be cashed and would be returned (or they would send a photo of it torn up) upon successful collection of the cylinders. If you know someone who has a French bank account and is willing to send you a cheque (which almost certainly won't be cashed) this helps; alternatively, you could open a Euro account with a UK bank (Barclays will do this, but you need to bank with them already). Failing that, you could just get a bankers draft in Euros from your own bank, but this is an expensive option (charges, plus losing on 2 currency transactions when you convert it back to sterling), whereas an unused cheque costs nothing.

You will need to ensure that the address you'll be staying in will allow you to keep medical oxygen there (for insurance reasons), so enquire before you book, whether hotel or rented house. SOS Oxygène have to deliver large cylinders [3000 litres] to a fixed address and pick up from the same address (it's illegal for you to transport the large cylinders by car yourself). Get more than you think you'll need, as the cost is the same, but another delivery/pickup if you run out will cost €115. If you're planning to travel around this makes things more complicated, because even though they can give you any number of portable cylinders which can be put in a car, these will only give you 65 mins at 15l/minute, so you may need lots of these and/or arrange a €115 delivery and pickup from another address (which *may* need to be in the same region that they cover). One last tip: they only deliver on weekdays, so make travel arrangments accordingly.

Website for SOS Oxygène:

https://www.sosoxygene.com/agences/?agence=1