Slitherine

In our game today we had another odd situation I wanted some input form others on.
The french had an artillery unit that was angled a bit off 90 degrees from a unit of Austrian infantry, so the infantry was at the end of the unit not quite a flank charge situation. The Austrians moved up so that they were within 2 Mu of the end corner of the artillery but were out of 2MU range of the artillery. At the beginning of the next French turn a unit of Cuirassier decided to charge the Austrian infantry.
Physically there was no room for the Cuirassier to fit as part of their front base would clear the artillery bases but they would otherwise end on top of their guns. Blathergut said he could simply push the guns back out of the way which he did.

I can't see any reference in the rules about such a situation so wanted input form others on how you think this situation should be handled thanks.

Page 40 (2nd bullet right-hand column and points under it): "...if insufficient space...non-moving unit may slide up to one base depth backwards..."

Now we did muddle that in another way: the cuirassiers didn't CMT to charge through the artillery.

didnt think they had to as they were shock

Shock do have to test to interpenetrate during an assault.
They don't test for being disordered or spent, but that's one they have to take.