Good value compost for containers?

[VelociraptorsVelociRapping]

My bank holiday job is to put together my container display. I have my pots and my plants (hostas, hydrangeas, lily of the valley, and astrantia if that makes a difference) and now need to buy some compost. I know about the tricks of using broken crocks and cardboard in the bottom of the pots but I will need some growing medium!

Please can anyone advise the best value place to buy compost? I looked in Aldi this morning and they had bags of standard compost at £3.49 for 40 litres, or seaweed enriched 'premium' for £4.49. B&Q Verve compost is £6 for 50l, three bags for £15. Are there any hidden gems that I am missing, or is the cheaper stuff a false economy?

Check how long the feed will last, it might be best to buy the cheapest and buy your own food to add to it.

I've bought from Aldi before but last year's seemed to be about 50% sand. I've bought more expensive stuff this year but haven't used it yet, so I can't comment on the quality

I've used the tomato grow bags for compost before now, and added some granular feed after about 6 weeks. They are usually relatively cheap.