I want to first of all thank all you that have had the time to both read my post and especially those of you that have provided your helpful reply - it has given me hope (in that this drug has caused this sudden decline and so hopefully we can 'pull' things back somewhat).An update for you is as follows..
Dad was given an appointment with his consultants nurse. To summarise he was told that 'it was matter of fact' that his condition and symptoms (particularly the new problems of sleeping and bladder that had suddenly escalated in the two weeks that his medication had been changed) was due in her opinion simply to the dementia. Mum was told that she put my Dad back on the memory drug Memantine and ‘try and tolerate it’. The main concern for my mum was that Dad was simply not sleeping and the shakes could not control. Again the reply was - nothing can be done so just carry on. At the time of the appointment he was not shuffling and could move reasonably well. The nurse commented that you seem to be moving well enough on this occasion so are you sure you have had problems with muscle rigidity??... (not the sort of comment you want to hear when the previous night he was on his hands and knees and could not move!)
Anyway unsatisfied by the outcome of this, an appointment was made with the family GP (who I have to say has been very caring, considerate and understanding throughout all of this). The GP was disheartened by the comments of the nurse and agreed that tolerating the the new symptoms of insomnia and bladder probelms was not an option. Subsequently he has arranged for blood tests for dads prostrate and also a urine test (as he had a similar infection only 2 months ago that sent him off colour). The GP has also prescribed Temazepam but with the caution that it may not work with the medication that he is already taking. I will find out how well he slept later when I go to visit.
My Mum has also noticed that the anti-depressants that the nurse had prescribed him to take last thing night have a side effect of insomnia so she is going to give him that tablet first thing in a morning (as he was originally taking until he was told to take it in the evening)
Fingers crossed an improvement will come about and that at least he can get some good sleep at night, and give him some quality of life back!
To date his medication is now as follows (with the exception of the Temazepam)
On waking: Stalevo 150mg / 1 Conazepam 500 mg
After Breakfast: Citalopram 20mg / 1 domperidone 10 mg
10:30 - 3 hours after first Stalevo: Stalevo 100mg / Fludrocortisone 100mg x 3
13:30 - Stalevo 100mg / 1 domperidone 10 mg
16:30 - Stalevo 100 mg
19:30 - Stalevo 100mg / 1 fomperidone 10 mg / 1 Citalopram 10 mg
TOTAL - Stalevo 550 mg plus 2 Madopar 62.5 Dispersable tablets when needed (which has been every day in the last 2 weeks!! Thanks for your time in reading this.