Good advice offered already,
We are in the middle of a heatwave, get down there take water temp morning, afternoon & evening, it may get too hot for trout. See if the EA can come down & take an oxygen reading for you or borrow a meter & do it yourself.
Is the lake spring fed or from a stream?
If its spring do the springs run all summer, if it’s a stream whats above you, any obvious pollution risk?
Whats the average depth? For trout to be comfortable you will need areas where you have a depth of 10ft or more.
Weed is it a problem, expensive to sort if it is.
OK is this a hobby or commercial, if your looking to make money have a look at where your customer base is coming from, is it a strong coarse fishing or fly fishing area. On the size of the water making money selling day permits for trout may not be easy, if the water is OK for trout then look at the possibility of a syndicate, no bailiff / manager wages.
Also if your thinking trout where is your nearest fish farm & the next nearest one, get quotes.
Check with the EA to see if there are any reported problems with the water, fish kills etc.
If your thinking it may be better for coarse fishing have a word with this group
www.pcfa.co.uk