Well, fingers crossed the infection seems to be clearing at last. Lump still the same size and appears to bother him at times so will continue to give metacam. Somebody at our ringcraft looked at it this week and said it looks like a hystiocytoma (her flat coats have had them) which is good news but will obviously still have the biospy done. Poor boy is bouncing off the walls with his lack of off lead runs but it's just too muddy and wet to risk it.
Thank you for all your good wishes, it means a lot to us. Will update more when we've seen the vet again x