It is 30% until you have your UTR number, but yes, at the end of the tax year you will be able to claim that extra back, along with any other allowable expenses.
The tax years starts 6th April 2012, so technically, you will be registered for self assessment prior to the end of this tax year, so will need to do a tax return.
It is also correct that self assessment does not mean self employment (we did write a blog on that) and during your period of PAYE you may also have incurred expenses that you can offset against your tax bill.
Of course, you can do this on your own, an accountant is not necessary, but, you may not claim for everything you can or indeed, have the implication to do it yourself. Obviously, if you need any help in geting registered, we happy to do that for you.