where can you buy fuses in the uk?

You can't buy them on the own unless you hold a licence to manufacture fireworks.Under the Manufacture and Storage of Explosives Regulations 2005 (MSER) individuals can store up to 5kg of Hazard Type 4 fireworks (generally Category 1 and 2 fireworks) without a licence and for an unlimited time. The Regulations also permit individuals to store up to 50 kg of Hazard Type 4 fireworks for private use for up to 21 days, without the need to licence or register. However, although the Regulations permit small quantities of fireworks to be kept without the need to licence or register, other requirements of the regulations - eg on storing safely - still apply.

If you have a Wilkinsons store near you, go there. They sell all sorts of fuses including 3amp. I think it's the best store in the town where I live. Products are good and much cheaper than elsewhere.