Mystery Pellet

Last while walking back along the track from the allotment I picked up a small bird pellet. Until this morning I forgot it was in my bag (in a pot). The pellet was very compact and had hardened since collecting so I only managed to pull out the largest bones. These I believe belonged to a Field Vole, with distinctive zig-zag set teeth, seen at x30 magnification.

I realised that most raptors produced pellets, but only recently discovered in fact almost all birds produce them. Does anyone have an option on what bird this came from? My thoughts are either Kestrel or Tawny Owl.