Hi,
I would say it was probably about 50-60foot long - probably enough for 1-2 pilots.
I could tell if it was a jet or prop as there was apparently no sound coming from the craft and I couldn't see any obvious engines or anything. I assume it was a prop - as I would think I would have heard it if it was a jet - even on tick-over.
Problem was it was a bright sunny day so all I saw was silhouette of it against the sky no detail.
Cheers
Adam.