Agree it does tend to get forgotten about and left in the drawer.
Unless your financial affairs are particularly complicated, you should be able to fill the form in with the information contained on the P60 you should have been given in April, plus any declared interest on savings ( except ISA's etc) and whatever allowable expenses you want to claim. Most of the form can be completed with a diagonal line through all the non relevant sections.
If you had submitted the form prior to 30th September the Inland Revenue would have done the calculation for you, however the onus is now on you to either do it yourself (there is free software available to help) or pay an accountant to do it for you. Best just to take a deep breath and get it done (quickly because the deadline is the 31st of January.)
As for asking an Inland Revenue Collector to fly a 757 ( I know you said an accountant) well I was and I do !
Good luck !