hello rich
just had a look for flights. sorry to ask do you know that biarritz is in france and its quite a way to pamplona?
have found flights from clickair.com who fly from heathrow - bilbao (150km and has a bus to pamplona)
dept. 6/7 lhr 16:40 arr. bio 19:30, dept 14/7 bio 14:55 arr. lhr 15:40, price for 4 incl.of all taxes etc... = 480 euros or £423. http://www.xe.com
better still easyjet fly from stanstead to bilbao. dept. stan 6/7 18:15 arr bio 21:15 dept bio 15/7 21:45 arr. stan 22:35, price for 4 incl. of all taxes and 4 hold baggage £345.48 (remember to uncheck their insurance)
i know you didn't stated rtn on the 14/7 but that is the best price with clickair.
now for the hotel, as you have probably found to your cost Rich. there are some hotels in pamplona with availability (not many) but prices start at about £1000 for a double room 6th - 15th. for the 4 of you £2000. the hotels are obviously charging the earth because of the bull run. i can understand why they would do this for a world famous event.
had a look at some of the youth hostel sites and they are charging about the same in some cases, CRAZY.
don't despair i have found a spanish site available in english http://www.reaj.com/index_en.html in the location search box they have 2 locations in pamplona for youth hostels.
1. fuerte del principle, click it, then re-directs to http://www.hihostels.com/dba/hostel051143.en.htm you have to email, tel or fax them. it looks ok.
2. residencia univesitaria los abedules, then re-directs to http://www.hihostels.com/dba/hostel051272.en.htm no contact detail. but found their site at http://translate.google.co.uk/translate?hl=en&sl=es&u=http://www.unavarra.es/servicio/ResidenciaUniversitaria/index.htm&ei=lJ7nSfTyI8W0-AbR37jmBQ&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3DPamplona%2B-%2BResidencia%2BUniversitaria%2BLos%2BAbedules%26hl%3Den%26sa%3DG the university looks great and maybe they have some availability at a good price? question whether your group qualifies (after looking at the site they take their own students but during the summer they take non-students?)
because theres no booking online it could be there may be availability at the 2 sites above. i have a gut feeling if you emailed them ASAP and get a reply in the next couple of days, the response may be good, but be prepaired for bad news that they are also booked up.
other than this i don't know what you could find Rich in the area? a campsite may be an option go to http://www.google.co.uk/search?hl=en&q=campsite+in+pamplona&meta=&aq=f&oq=
also found this site with good info
http://www.pilotguides.com/destination_guide/europe/spain/pamplona_bull_run.php
regards
jim