Cognitive / Non Specific Problems

I'm a 34 year old U.K male, who, in December 2008, started to notice mild issues with concentration and natural thought process, but didn't really think much of them initially. However, these issues continued to progress to the point, that by March this year, I had to leave my job, as I was no longer able to manage daily tasks (office work), given my decline in cognitive abilities. By this time, my short term memory had also become quite poor.

Aside from the cognitive issues: natural thought process impaired, getting confused quite easily, feeling disoriented, and short term memory issues, the only physical manifestation of the problem was increasingly incessant muscle twitching, and periodical problems with balance. Now, since around July, I've also developed shooting pains down both my arms and legs, and the sensation of both pin pricks and crawling on my skin, not to mention, terrible insomnia.

I was sent for an MRI of the brain back in May, which came back normal, and most recently had the following lot of blood tests carried out, all of which were normal: Thyroid Profile / T3 / Cortisol / Glucose / HbA1c / ACE / ANA / ESR / CRP / Lyme / Calcium / B12 / PTH / Folate. I've also had Coeliac disease for about 5 years, but is fully under control, as verified by having a repeat gastroendoscopy last month.

To date, I've seen 2 neurologists, one in April, and the most recent one last month, both of whom performed what I presume are the standard neurological tests of walking in a line heel to toe, reflexes, looking into eyes, etc. Both assured me there were no signs of any serious neurological illness, and alluded to the causes of my symptoms, being 'psychological'.

So now, after not really having any life at all throughout all of 2009, my health continues to decline, and I'm still no nearer to obtaining any sort of diagnosis. Any insight into possible future tests or investigations to request, to try and get to the bottom of my symptoms, would be much appreciated.