I do mine myself, after learning from picking the brains of my tax guy for a couple years. I'd tell HMRC to communicate with you not your accountant from now on. HMRC will then send you automatic reminders of deadlines. They also send you How to Guides and helpful webinars
Ask him to hand over all documents relating to your previous tax and returns if he hasn't yet. Keep those for your own reference, so you know your tax history. I pretty much copied what my accountant did in previous forms.
HMRC will help you over the phone with filling in the forms, queries, dates and deadlines. If you complete your tax form before the deadlines they work out your tax for you immediately before you finally send it in. You can always correct any errors or go back to fill in questions before you 'send'. I find them very helpful when I ring up.