Data cleansing

This job is for cleansing phone numbers on a UK database.

We have a list of about 800 old customers/contacts with either a) no phone number or b)the phone number doesn't work.
I estimate about 20% are still live/traceable businesses. The remainder are gone-aways or ceased trading.

Therefore research is needed on the internet to try to locate as many phone numbers as possible.

Data will be supplied as an excel spreadsheet.
Tests show that around 50+ records can be cleansed per hour using companycheck.co.uk (or similar) and google.

Sample file attached.