Does Red Nose recommend the use of a baby monitor/breathing device in a bassinet noting that the sensor pad does cover some of the ventilation holes under the mattress?

There is no scientific evidence that using a monitor will prevent Sudden Unexpected Death in Infancy (SUDI)
However, there is no increased risk in using a home monitor.

Many parents, aware of the risk of sudden infant death and wanting to provide the best possible care for their child, may consider the purchase of a home monitoring system for their baby. This may also include parents who are expecting a baby following the sudden and unexpected death of a baby previously.

All alarm systems, however, have been associated with false alarms and babies have been found dead without the monitor alarming. Many babies experience apnoea (prolonged pause in breathing) and a slow heart rate exceeding the alarm thresholds and do not die. This may cause multiple false alarms.
A link has not been established between prolonged apnoea and SIDS.
https://rednose.org.au/article/home-monitoring

​While Red Nose does not recommend routine home monitoring for all babies, there is comprehensive information on the different types of monitoring systems available here.