Went in-store to my local B&Q (Nottingham) and they had this mower MPRM 53SP on sale reduced from £315 to £216. I went home and found it for £155 on B&Qs own website, although out of stock online. It does say check local store availability but came up with none in stock, however I had seen them in store. I went back the next day to B&Q and showed customer services the webpage along with product code and when they put it through the system it came through at £155. Yesterday there were about 6-8 in stock still.
If you are interested in these, I suggest head down to your local store and check the stock rather than use the online search as it will likely show none available, or give them a call. If your local store stocks these then you can make use of this offer so it's potentially nationwide.
Its a big lawnmower for a low(ish) price. Don't know how long the website will display at this price so I suggest move quickly.
Also if you are over 60 years old I think you get 10% off on a Wednesday through their Diamond Club scheme.