Sorry matey!
First thing that comes to mind is head gasket failure, because my head gasket blew a few times last year!
The "tell tale" signs don't alway apply,
Check the coolant level before you start her in the morning, if there is to much in the expansion bottle, that's bad!
Let her tick over for a while, watch the temp rise, and the fan should kick in! if it doesn't then then hopefully that's all it is!
If it does, and the temp still rises, then it's hopefully the thermostat, to check that, take it out, Follow the bottom rad hose to the engine, loosen the pipe to drain coolant and remove 3 bolts, and open it up and remove the thermostat, put it all back together, fill her with coolant, leave the cap off and keep filling untill she takes no more, and see if she over heats again!
If she does, it aint the thermostat!!! it's the head gasket!
She may need to be driven or given a bit of stick to make all happen
Best of luck man!
Where are you based,
Dan