Hi Sheila, There is a product called EMLA - comes as a tube of cream - to use when you clean the ulcer out. Should be available OTC or to order from your local pharmacy. Put some on and cover it with cling film or OPSITE FLEXIFIX (Smith and Nephew) for at least an hour before you debride/clean out. It numbs the area and will wear off after two hours or so, so will start to hurt about then. I also take Paracetamol/codeine about 1.5 hours before a debriding session.
Another numbing cream which is less powerful is Lidocaine, used in the same way. I also use compression stocking to hold the pads in place, rather than plasters. The skin is so fragile.