Is Groupsave available via the third party apps, such as Trainpal, Ticketsplit, Trainline, etc, etc?
Our site (powered by Trainsplit) will do it!
If so, makes sense to just use one of those, rather than a specific operators app for tickets.
The problem is that companies like LNER have access to taxpayers' funds, to implement incentives for people to purchase tickets through their website.
This entices people (such as the original poster) into wanting to use those websites, rather than ours, even though the prices charged may be higher on LNER than what we charge.
We don't have taxpayers funding our site to give away cashback, however what we do have is a system which often finds cheaper combinations of tickets than the through fare charged by train companies, and a free seat selector (where applicable).
If anyone uses our site, they would get access to discounts such as GroupSave,
and would be paying no more than the price charged by train companies (indeed in some cases, we will charge less)
and you would also be helping us maintain the forum and associated activities. We are very grateful for people using our site, and this contributes a four-figure sum each year towards our costs (we run on a not for profit basis).