In order to get rid of bedbugs the whole room when they have been discovered in needs to be taken apart before it is sprayed.
A rule of thumb is... if something the thicknesss of a piece of paper can be pushed in, bedbugs can hide. This means removing electrical sockets and switches, taking all beds and all other furniture apart and pulling up fitted carpets at the edges to allow for full spraying to be effective.
Bedbugs and their eggs are incredibly resilient and only temperatures of 60C and above will kill them so curtains and bedding need to be washed at these temperatures and above. Bedbugs can also survive a year without food so these make a very formiable pest.
Almost certainly between two or three visits are needed to control this pest as they are very hardy and almost impossible to get rid of these pests without professional help.