How much does it cost to have a pet dog trimmed and bathed please im in Dorset.

For me it would depend on size, breed and condition of coat.  

The dogs are a miniature schnauzer and a miniature poodle, & they are regularly groomed so no matting in the coat.

Mini Schnauzer with just body stripped and the rest done with thinners, £28. Mini Poodle in a basic lamb trim with full legs, £26.

Thank you.

Forgot to ask, how long does it take to trim these two breeds?

I would ask the owner to leave them for 2 hours each.