Previously I was using average quality B&Q brushes @ ~£2.50 and cleaning them afterwards with acetone but now I'm using EC 1" brushes @ ~£0.30 each and disposing them after a single use .  They are far cheaper than the cheapest B&Q brushes I could find.

I buy a bulk pack, they end up costing about 16p each. I tend to reuse them, not because of cost but for environmental reasons. I keep a tin with brush cleaner with about 10 brushes in it, then pick one when I need one. The only time I use a new brush is when gel coating.

I do exactly the same ..