Many thanks for the reply. From research, it seems that corrugated pipes are an absolute nightmare to get watertight and the problem revolved around ensuring that there was a watertight seal between the corrugated pipe and the waste connection.
I have managed to solve the problem and if anyone's having a similar problem can suggest: purchase rubber waste-pipe ends, together with some silicone gel and plumbers' tape (the membrane type stuff). Attach the corrugated pipe to the rubber end and fill the join with the silicone gel. Wrap the connection in the plumbers' tape and add some more silicone gel to the tape. Let the gel dry and, presto, there should be a watertight seal between the corrugated pipe and rubber end. Then fix the rubber end to the waste connection on the sink with a jubilee clip.
It's all holding up so far -- fingers crossed.
Many thanks for your efforts, Andy.