From what I remember of DH being an executor on a couple of wills, 'Too much'. If a particular solicitor is actually named as an executor, theres not much you can do about it, but otherwise, you can negotiate and find one who will (if its better for you) a fixed fee or hourly rate.
Not all solicitors charge a percentage, many will charge by the hour. It is always advisable to try and sort out as much as you can yourself, so that you aren't paying a solicitor to do work that you could easily do yourself (e.g. informing pensions providers/banks etc of the death).
As Lilymaid says, most will charge an hourly rate. My mum's estate is just going through probate and the charging rate is £200 ph plus VAT. I did as much of it myself, ie informing banks, pension company etc) but had to leave the lawyers to do the rest as I just wasn't up to doing it.
I read the article, it's quite shocking really. How can they get away with that?
Unfortunately the solicitors have been dealing with it for that last 7 months so there will be no chance of changing that now. The estate is worth 400,000 so looks like the solicitors are going to get a huge cut.