Keeping a conservatory cool? Any ideas?

[KatyMac]

I have (DIY) roof blinds, roof windows/vents & opening windows

It is always hot

HELP?

I'd suggest a roof with proper tinted thermal roof glass in it. It cuts out a lot of the heat.
We have had thermal glass (Pilkington Activ) and 2 opening roof vents on a N-facing one with absolutely no problems, in the midlands not a single day was it too hot to use (I used to work in it, almost every day one year when I was on a book project) and we had no blinds at all.
We are just having a S-facing one here n the NW with the same glass, similar size but four opening roof vents, plus 4 casements and four toplights and 2 sets of doors. Not had the hottest days in it yet but it is definitely cooler than being outside in the sun (still no blinds). Neutral Active, the one we have cuts out 72% of the heat, if you get the blue version that cuts out more.
I dislike solid roofs on conservatories, they make the conservatory dark and the inner room very dark, and for me the whole point of the conservatory is that it it very, very light and I can see the sky.
As it faces S, I suspect a few days a year it will be too hot, just as sitting outside in the sun would be, but in my experience up here in the Pennines that's going to be only a few days a year. For me, conservatories are at their very best in Spring, autumn, and sunny winter days, when they are warmer than the house and can be used like a radiator- and for those of us who get depressed and crabby on dark days, they are a godsend because of how much more light they let in than internal rooms.