Ah - so I know my two were both told that ‘as a rule of thumb’ best to take the highest and lowest offers as firmed and insured, and where grades are close across the board, look for at least 2 grades differential. My DS had all 2xAstarA or AstarAA offers (we took the view that we would look at clearing if it all went belly up as Lancaster and Surrey etc also had places in clearing, (including via the foundation year if things went seriously bad).
However, I would advise that he checks with Southampton what the implications are because they are really very flexible - I know of much desired candidates getting in with ABB after offers of 2Astars/A because their references/statements and past grades were so strong.
Am just pasting this from Southampton’s email entitled ‘Flexibility on Entry Requirements’:
If you don’t yet know your exam results, we want to reassure you that for some subjects, we may be able to show some flexibility in the grades we accept, even if you don’t meet the academic grade conditions of your offer.
There's nothing you need to do. If flexibility is possible, it will be applied automatically when we review your results.
When we made your offer, we considered a range of factors to make sure we were confident in your potential to thrive at Southampton. These included contextual information, your predicted grades, the subjects you’re studying, and the grades we’ve accepted in previous years.
You can see the highest and lowest grades that our previously enrolled students achieved, on your course page on the UCAS website.
Not sure if this is helpful?