Sorry to hear of your predicament.
From a formal position, if they 'signed off' on the deal based on the products/samples you showed them, you are probably within your rights to refuse to collect/refund(subjects to any supply contract they have and you agreed to, although it looks like you have nothing but verbal agreements!).
HOWEVER, this is not a way to build the business!
I suggest you take the following actions:
If they will not stick them on, logistics permitting, you go stick them on. This will give you the opportunity to show them how committed you are to there business!
In the bigger picture, many retailers, even smaller ones, use EPOS systems that are driven by bar codes, so, in the longer term, it is beneficial to register, especially as it may get you into a few more places!
However, it is understandable that even a few hundred quid may be too much to think about, but, if you are serious about growing, you will need it sooner rather than later.
I hope this helps,
I'm really sorry to hear about your predicament. I guess you'll realise from this that putting things in writing is always a good idea, both to protect you and your customer.
Personally, if it's possible, I'd try to salvage the relationship because it's in his interests to source good stuff to sell, eg: your food and it's in your interests to have an outlet who wants to source your products.
To avoid having to give him a refund, you could offer him a small discount on the stock, (if you've got enough leeway) and I'd consider seriously whether breaking even on this batch might mean that you'll be able to make a profit on future sales, assuming the relationship survives.
However I would defend your position by saying that had he mentioned the need for barcodes at an early stage this would have not have been a problem at all.
In terms of obtaining barcode numbers for your use, the organisation as already mentioned is indeed GS1 UK, (http://www.gs1uk.org). The cost is, (for organisations with a turnover up to £500,000 per annum) £102.00 to join plus £102.00 annual subscription. Included in this cost are as many numbers as you want. These have to be issued by the agency because the first part of the number relates in an intrinsic way to your particular company.
In terms of generating your own barcodes, please don't waste your money on a program that costs £20 to get a professionally produced barcode because you'll be wasting your money. To get the correct barcode you really need to use professional barcode authoring software, which of course isn't cheap at all.
We do have access to this kind of software and if you wanted some barcodes produced we'd be able to do them for you at a cost of £2.91 per barcode. If you were after a whole batch at the same time we could probably improve on this price slightly.