...so have you any tips to getting the facia off. Thanks
Yes, don't try and force it off, because it's not meant to come off!
The clips may be broken at one side, hence it being slack, but the facia can only be safely removed once the entire headunit is removed.
You need to remove the headunit by inserting the 'tool' into the four holes, two at either end of the headunit. You will of course have to remove the grub screws from the holes first.
With regard to the 'tool', i've always found these to be pretty poor, i always use ball ended allen keys for removing units, never fails.
Also, when you are trying to remove it, don't pull on the facia, or try to prise it out with a driver, no matter how tempted you are, you'll only damage it. With your 'tool' inserted and located properly, you push each one away from the centre of the unit whilst pulling at the same time. ie. the left to the left and the right to the right, while pulling towards you. If the tool, or allen keys are located properly they shouldn't come out.
It is tight, but it will come with a bit of patience.
With regard to the screw you tightened, remove it completely and see if it makes a difference.