there were 6/7 fields last year 4 large and 2/3 smaller and sorry cant remember the names
There are generally loos in each field as well as the central area- re the fields there is one large one which has fantastic sea views and no cars except for drop off/pick up but is quite slopy and has the coast path (and cliff edges) on the side probably has the least number of toilets!
the next field up gets the busiest as has sea views but you can take cars
next is another large field which is probably the flattest so also gets busy but still plenty of space
next field is the 'corner' field - furthest from the sea - quite flattish along the hedge but very slopey as goes up a hill - you can see seaviews/Weymouth fireworks if you walk up the hill it is also more protected from the wind...and also has less traffic as is route to nowhere we have pitched here both visits due to travelling with small kids and felt safer as nowehere for them to go 
I wasnt so keen on the smaller fields as they get more people driving through them-didn't really look at the field opposite reception - but you'd have a big view of the carpark!
as people come and go at all times its best just to drive around until you see a spot you fancy or notice some people packing up and wait..
if it gets really wet you can park in the village near the church and walk along the footpath as the road in is quite steep
sorry for the essay, the toilets are cleaned frequently and if you're happy to use the composting loos you'll should never have to wait!
hth