I can't give a personal recommendation but I've just checked my favourite site for budget accommodation:
http://www.hostelworld.com
Don't be put off by the word 'hostel' in the name. There are plenty of hotels and guesthouses listed. One of the great things about that site is that all accommodation is awarded marks by their customers. (When you first get a list of available accommodation, some hotels don't show a customer satisfaction percentage. This is only because fewer than 6 people have awarded a score in the last 6 months. If you click on 'details', and then on the all-important 'Ratings' tab, you'll still be able to read some reviews).
Give it a try yourself. Go to the link above. Put in the relevant details and then click on 'Additional search options'. Select both 'Budget Hotels' and 'Guesthouses'. You'll be presented with an extensive list of possibilities. From those, the one which really caught my eye was the ABC House. It's got exceptionally good reviews (which can be accessed by clicking on the 'Ratings' tab, at the top of the page, when you visit the page which gives details of the accommodation). It also seems to be well located. Prices for B&B in a single room with en suite facilities are between 60 and 65 euros per night.
Hoping this helps,
Chris