Dave, I bought a 25 litre drum for about £80. It is expensive and if you are doing a fair mileage every few weeks Super Unleaded E5 will be fine, but I do more sporadic runs which means the bike can sit for a month before another big run.
To be perfectly honest it was the smell of E5 / 10 that really put me off using it. Its paint stripper smell is just too much and it quickly goes yellow after a couple of weeks. I am sure technically it will be fine but the smell in the garage was making me feel ill.
What I can say is that Aspen runs the engine nice and cool, it doesnt smell, its a very clean fuel e.g. far less nasty stuff in it... but it comes at a cost.
I have no other vices in life, dont smoke, gamble.... occasional beer etc... so why not. As my late father reminded me, there are no pockets in a shroud!