We are all pretty good at loft insulation but have you insulated your loft hatch and sealed it around the edges to prevent drafts?
One way of doing this is by using old carpet and flooring underlay.
Insulated loft hatch
The next stage is to fit a new, insulated loft hatch (pictured below). This is a bigger job but the new hatch will have a very good draft seal already fitted.
Put another layer of insulation across the top of your joists
Accepted practice for loft insulation has changed over time
Only a few years ago, 150mm of insulation (between the ceiling joists) was good practice.
The current recommendation is to put another layer of insulation across the top of your joists – an extra 170 or 200mm is enough. These “top up” rolls of insulation a readily available at most DIY warehouses or online.