Roof fix ideas - converted loft too hot

[MRex]

The previous owners had the loft converted, so we don't know exactly what insulation is in the roof. It is superficially ok in winter; we're probably losing more heat than we should, but mostly it's only noticeable if we open up the eaves cupboards. In summer though we bake. Even with the blinds down and windows open later on it's still 26 degrees up there. The rest of the house is fine. The converted room is big, it has one slopy roof and the rest is a big box, a flat roof on top. Apart from the eaves there's nowhere obvious where we can get at the insulation inside.

Any ideas what we can do? The eaves are low, so is insulating them any use at all for heat?

Thanks, this is all great stuff. I'll try to get hold of a thermal imaging camera, but we could definitely improve insulation in the eaves because we know they're very cold in winter (we used draft exclusion tape by the doors, but thinking about it that won't help much with heat). Plus we can try to insulate the velux gaps. Then we'll see what happens with the temperature after that. Thanks for your help, I'll be back in a.few weeks when we've done some initial steps.