There really isn't a problem with supplies of pellets in the UK.
The Louisiana Grills brand are readily available and come in several varieties (alder, apple, cherry, hickory, and mesquite). I have had great success with both the apple and cherry varieties. Apparently, they are manufactured by the same company who make Lil Devils, but I found their smoke taste more pronounced.
They are no more expensive than the pellets Jackie was importing, so there has been no price hit in moving to them. Enough UK companies are stocking them that I have no worries about continuity of supply.
Why I am experimenting with the Lil Devils pellets is that Liverpool Wood Pellets is selling them at half the price of all other imported brands on sale in the UK. Also - as LWP is in the (heating) pellet business, I can't help thinking that if people buy from them and show there is a demand, they may also get into manufacturing their own food grade pellets, which can only be good.
Regarding economies of cooking, I estimate that my Traeger uses 0.5lb/hour when in smoke mode, 1lb/hr at medium (325 F, approx) and 2lb/hr on high. This means that the Louisiana Grill pellets work out about 50p/hr to smoke and 2 quid an hour for cooking on high. The Lil Devils will work out at about 25p/hr to smoke and 1 pound/hour for cooking on high. I think that is probably less than I was spending on charcoal to keep my Weber kettle going.