There's nobody actually in Worksop I don't think that would be able to deal with a horse vetting but you could try Park Hall at Mansfield (Margaret would be best if you can get her) 01623 620784.
Or you could try Minster who are based in Doncaster I think & they will travel out 01302 864767.
You will have to find out who his usual vet is as I don't know if they can do vetting for you - conflict of interest & all that.