Well, she's probably preggers. Yo can get various birthing nets, they hang on the side of the tank. Several different designs, don't know what's avaiable to you in the UK. Some are made so you put mom in, and the babies will fall into a separate chamber after birth, so neither she nor any other fish can eat them. Other kinds are a simple net, mom and kids stay together, but she might eat them.
I always had just the net, and would let mom give birth in the tank, catch as many babies as i could, and put them in the net. Mom would never cooperate and do it while i was home, so mortality rates were high. If i ever get livebearers again, I'll try the 2 chamber type.