I bought GO Isotonic Energy Gel - 30 Pack (Blackcurrant)
Save 50%
Special Price£22.50 (I bought 2 packs so no postage).
So Lidl is a bit cheaper but there are no Lidl near me (Lots of Aldi!)
If you get on the SIS email list they are always offering special deals.
I once bought bulk boxes of gels that were meant for the US market and were printed with US data but I think were within a year of the sell by date** and presumably could not be shipped there for sale - or something - and so were ridiculously cheap.
** I think there were so many I didn't get through them in the time - but (as you see) I'm still here!!!