Hi Steve,
Defo a good starting point to recanvass your old customers, if you still have their details & numbers you could do this over the phone to save you a bit of time, then if they want a price arrange to pop round.
If you are going WFP then TBH you would want to look at a 6-8 week schedule, IMO with current economic climate you will probaly have more success with every 8 weeks.