There's no way to answer that without knowing where you are, what you're likely to be doing and what sort of records you will keep.
An accountant in Central London will charge a much higher hourly rate than one in rural Scotland. If you have a few dozen transactions over a year and nothing complicated it will take far less time than if you have hundreds of transactions a month and don't keep great records.
You could have a massively complicated business but keep your own excellent records and present effectively accounts to an accountant to check and work your tax out from annually and end up paying far less than an oddjob man with a shoebox full of invoices because his takes longer to actually sort out.
Could be anything from �100 to several thousand depending what's involved. If you are competent to fill in a few forms yourself and don't have anything particularly complicated tax-wise you could indeed deal with everything yourself and not go near an accountant.