Hi, we found a long standing leak in the copper central heating pipe which was buried in the concrete floor. Plumber came out & removed the bit of pipe with the leak & adding a replacement bit in using copper pipe & joints. Initially, he left it so that one corner of the pipe was proud of the surrounding concrete floor & therefore we could not fill the hole & level floor. He came back today & used a metal strip with holes in to pull the pipe down. This evening with the heating on, the pipe has a tapping noise that comes & goes. It did not do this before he tried it down. So I have two questions: 1. Is this tapping noise okay, will it go? 2. How do we fill the hole, (we will wrap the pipes with tape first). What mix of concrete, can we use a product from B & Q, this one... https://www.diy.com/departments/u-can-patch-fill-concrete-repair-5kg-tub/258255_BQ.prd?rrec=true Do we need to paint the concrete with anything tacky first? Really hope you guys can help. Photos attached.