Delays with searches are a constant concern to estate agents. At times we have known them take up to nine weeks to be done delaying completions and leading to increased numbers of sales falling through.
Different councils often perform differently with regards to turning around searches. In the area at the moment two to three weeks is the norm, however, West Dorset District Council is taking up to 45 working days (the grapevine informs me).
Always take your solicitors and estate agents advice when applying for searches. Delaying can cause pressure at the end of a sale.