Are you sure that you actually need a counter-signatory? Most people don't. From what you've written in your post, it's clearly not your first passport. You've also made no reference to losing your old passport or to having had it stolen or getting it damaged. So, unless your facial features have changed so dramatically that your new photo can't be recognised as an updated version of your old one, I can't see why you'd need a counter-signatory at all.
https://www.gov.uk/countersigning-passport-applications
I most definitely didn't need a counter-signatory when I renewed my passport last year. I just had a photo taken in one of the newer booths, that give you a reference number with your prints, completed the online form in a few clicks (including the photo reference number), authorised the payment and then sent my old passport back when asked to. It was all very simple.