First post so no doubt I'll have got this horrendously wrong.
Found this deal in store in Homebase today. 9.2L sized tub for the price of a 4.6L. Fixes and grouts up to 8.2m² , waterproof with 5 year stay white guarantee.
Looks like in store only as showing as £14.99 for standard size 4.6L tub online.
Same size tub is currently £25.98 in B&Q.