Unless you are modelling open countryside, at least one shop is likely to be needed. Many towns have shops in different architectural styles spanning several decades. The Kingsway Models range of shops reflects this. 

Many of the buildings are described as having 'traditional' or 'modern' shop fronts included. Inevitably such descriptions are prone to become meaningless!  Generally, you may take 'traditional' to be from the middle 20th century, and 'modern' to be from the 1980s onwards. Obviously there will be overlaps of period. The buildings could quite easily be fitted with customised shopfronts if required.

The never ending range of potential shop models appeals greatly to me, so doubtless the range of buildings listed here will continue to grow. As you seek to fill your model High Street, do remember to look at the other categories as well. Cinemas are hard to resist, or maybe a pub - there are examples large and small. The miscellaneous buildings page may have ideas that will be useful.