For economy filament I would recommend Sunlu, and pay rather less than £20 for 1kg of PLA +
I seriously recommend PLA+ over standard PLA.
There are plenty of good brands out there at reasonable prices, and truly 'bad filament' is a rarity these days.
For 'tip top' results pay the extra for the big name brands, but the improvements are marginal if your printer is well set up.
If your printer isn't well dialled in, cheaper filament seems more likely to result in clogs, missed layers, stringing or poor adhesion.
Neil