STOVES fan oven - inlet fan on regardless HOB GRILL or OVEN

First things first. The top oven lights ONLY come on when the top oven is switched on. Operating the grill DOES NOT turn the lights on. If you wish to see what you are grilling, you have to turn the top oven control knob on to its first position as well as turning the grill on.
Secondly, the grill only works when the door is open. The grill does not work when you shut the door. When you open and shut the door, you should be able to hear the microswitch operating. It is located in the right hand side of the cooker, between the inner and outer panels - you cannot see it. I haven't seen the switch first hand but they normally come with an arm that contacts the door mechanism and the door mechanism operating, causes the arm to move, which causes a button on the switch to move and make the circuit. It has been known for the arm on the microswitch to bend with use so it no longer works correctly.
If you have checked all above and you hear the switch operating, then it could have failed. They are quite common, so if you can't get one from STOVES, try espares or someone like Maplin or RadioSpares.
The get to the microswitch you have to take the oven out of the housing and then take the right hand panel off. You should then be able to see it and check its operation.
All the best

Post your email address and I will send you a pdf copy.

The double oven will only work if a time is set on the clock. Any time will do, you just have to set a time. The grill/top oven is independent of the clock. If the clock is faulty espare can sorce them for you.

stoves df50 gas hob lights,but only gives a flame,help

First things first. There are two fans. One in the bottom oven and one to provide background cooling. The background cooling fan turns on when anything is turned on. (Fan oven/top oven/grill). Just operate the top oven for a moment and this should cause the cooling fan to operate. There is a printed circuit board that controls the cooling fan and for how long the fan should stay on once everything has been turned off. (About 7 mins). If this fan is not running then the fan/motor could be faulty, or the circuit board or the resistor on the fan terminal block. The reason the oven will not turn back on is that the residual heat in the oven unit as a whole against the fan oven, is probably too high which causes the overheat device to operate.
You will have to take the oven out of the kitchen carcass, take the top and rear panels off and get an electrician to test and found out which item is not working/failed. Try espares for parts.

The hob is normally totally independent of the oven. What is actually working or not working on the oven? i.e. does the grill still work, is the clock OK and can you set it, or is everything totally dead?

Press the micro switch located just behind clock on top surface. Little red button with two wires coming from switch.

When you say the main fan, do you mean the background cooling fan or do you mean the circulating fan in the bottom oven?
Do you have the handbook for this oven as the wiring diagrams are included in it. If you haven't, you can take a copy from my BT Digital Vault - all I need is an email address to register you.
Looking at the diagram, the power for the cooling fan comes via the timer board. If, as you say, the fan doesn't work at all, the timer board could have gone faulty.

check your manual if you don't have one check the internet for your model and download and then print it out.