Start by just forcing yourself to think about spiders. Start with the spiders you find least offensive, then move up to the ones you find most disturbing. When you feel comfortable with the thought of them, start looking at pictures of them, then when you can deal with pictures, move onto watching videos of them crawling around, mating, feeding, whatever. From there, move to observing them in a tank or terrarium, then observing them in nature. Keep pushing yourself with closer and closer encounters. Tap the web and watch it scutter away, or hold your finger out to it. Eventually you'll want to coax one onto your hand, (ID it first to ensure it's not venomous or aggressive, although that's probably not neccessary in the UK), and when you're comfortable with all that, provoke a less-dangerous species into biting you. That's the basic recipe for dealing with any phobia, anyways. Start small and work your way up, even if you never get to the final stages of handling and being bitten, you should at least cope far better with spiders in the same room as you. If you don't have the willpower to force yourself to go through the first few steps, then I'm sorry, but you're going to be stuck with your phobia.