B & Q do some, they don't seem to be on the website at the moment but did a reasonable cheap "overlap" range. As clubman says 6 x 4 is small. they did 6x3 (think of a pool table) and 7x5 for approx €160 and €180 (self assembly but very easy) If you ask in store they may be able to order. When I asked the guy knew nothing, but when he went to computer there was a list of codes handwritten and taped to bench beside it!
Just overlaped timber, nothing fancy, small bit better quality than fence panels, but if its what ur after.