There can sometimes be a bit of confusion about needing visas for Egypt as some areas state they are not needed where others are mandatory.
Sharm El Sheikh, Dahab, Nuweiba and Taba resorts can be visited up to 14 days without needing a visa, however, if you decide to venture out of these resorts, then you must have one.
You can purchase a visa at the airport on arrival but expect to be hounded by the reps who try to push you towards their own visa kiosks where you will pay more. You are best to ignore these people and head straight to the official bank kiosks who will charge you the correct amount which currently stands at $25 for UK Citizens. You can pay in Sterling (around £15) but you may need extra in small change depending on the exchange rate.
If you do not want the hassle of queuing up for the visa and then queuing again at passport control, you can purchase the visa from the Egyptian Consulate before you travel.
This is very easy to do by entering the website, downloading the forms and filling them out on the computer, printing them and sending them off with your passports, 2 passport photos and the correct fee which is £20 each from the UK. Yes, it is more ,and you have to pay for special delivery for both your form being sent and the return envelope for them to send back, but we had ours back within 10 days and it was so nice to walk past all the queues at the airport not having to worry about the reps trying to push us to their kiosks.
You will still need to fill out an immigration form that may be handed to you on the aircraft or you can obtain one at the airport and hand this to passport control also.
The Egyptian Consulate site is http://www.egyptianconsulate.co.uk/home.php