Printworks is disgustingly expensive as I recall and to my knowledge Lafrowda is basically on the Streatham campus, so less ideal.
You may want to consider UNITE - Northernhay House is in town, and a not too long (but all uphill, as with everything in Exe
) walk to the main (Streatham) campus, and a (maybe) longer walk to the St Lukes campus. Crucially though, it's about a minute away from the central bus stops (where the buses stop for about 5 mins) where the D (I assume it's still the D) goes to both campuses (although which side of the road you get it from will depend on which you're going - you want to be on the Next side for Streatham and the same side as Northernhay for St Lukes).
Alternately, the UNITE Exeter Trust House is pretty equally between them, but probably less convenient in terms of buses or walking to either... you're not on the D bus route there, so would need to get a dayrider and hop buses in town if you wanted to do that, and walking is a bit longer to the main campus and while not that far as the crow flies to St Lukes, it's sort of weirdly parallel to the campus and may not have ideal walking routes between them. Also it's a bit of a rougher patch there anyway...
I'd probably say Northernhay would be ideal, walking to the main campus (or bussing if you oversleep
) and bussing to St Lukes (or walking actually - it's not really that far from there anyway if you go down past the Vue way, it would probably take about as long as the other walk as it's slightly flatter that way too). You're also directly in town, saving you taxi money on nights out, convenience for shopping for grocery bits, etc, etc. Also if you're on the north/east side of the building, you can look out your window to see if you're too late to get an outdoor table at Firehouse (the answer is always yes, but at least you'll know not to be disappointed on arrival...)