Thomas Proctor and Son on Durranhill in Carlisle did supply UK oxygen I think and may still do so. I use BOC at home and the guy I work with has changed to them as well from UK oxygen, I have no problems with BOC. I think the depot at Workington is open on Saturdays to.
The old "licence" is an urban mith, but you do have to pay an annual rental charge - bit like your BT phone line rental. Prices vary depending on cylinder size; 0800 111 333 is their central number that will put you in touch with a local depot (If they were sharp enough they'd be offering a forum members discount in the weldequip shop, but I think that'll probably come down to a more enterprising 'new entry' in the UK gas market in the end ).
Just got my bill, I use BOC at Carlisle changed 2 Argoshield universal size Y bottles last week.
£35.65 each for the re-fill
.90 environment surcharge
£11.35 fixed charge
So the total for the above including VAT is £99.24, fortunately for me I am VAT registered.
The Rent is also due and it is £74.40 per bottle for 12 months, + VAT