Group plan v double data offer

I’m looking to transfer 4 more sims to Smarty from O2 because of their price increase of £2.50/month in April. I have a Smarty 80GB/month sim with unlimited calls and texts at the moment for £10/month and could separately transfer each of the sims to this plan as it is on offer at the moment. However, I would much prefer to use a group plan arrangement as this is what I have with O2 at the moment - and these benefit from double data (as I’m also with VM). Unfortunately, if I try to access the double data 80GB/£10 month with Smarty with the group plan then only 40gB is available. Is it possible to get the group plan with 80GB data for £10/month with the group plan.