I use this - Draper 69690 320-Litres-per-Minute (Maximum) 230-Volt 1,000-Watt Submersible Dirty Water Pump with Float Switch - £129 on amazon at the mo, which is a good price, as i paid £170 odd a couple of years ago for mine, this was the fastest pump for the money i could find at the time and still think it is? ive had mine submerged in a 1000l ibc for about 3 years and its is still fine. It takes about 15mins to fill a empty 500l tank, pumping down a 20m or so, of 1" braided pipe
100m meter transfer is a long way, so it will be slower on your fill up, but the higher lpm the better. There is a 261lpm einhell in tool station for £54.99, but its a little slower, btw don't be tempted to use that cheap poope 1" black pond hose, as it will just tear when u pull it around, 1" braided is the best with geka fittings, or 1" lay flat pipe is ok in a straight line. good luck m