Ivy,
Mrs Holden's shop sold bread and milk (but not much else!), but perhaps you are thinking of Mrs Jones' shop at the corner of Cooksey Road and Oakley Road, opposite the school. She used to bake rock cakes and jam tarts, etc. Graham Edmunds took over this shop years later for motorbike repairs.
I have written and published seven books myself, including the one illustrated here which may be of interest to you. Its only sold through the Symphony Hall Gift Shop, Broad Street, but if you would like a complimentary copy perhaps the Moderator can put us in touch via email?
Boomy (Norman)