Long planks of wood (BN11 worthing)

Hi looking for couple of long planks of wood to make shelves.
-Minimum width of 19.5cm/195mm
-No deeper than 2cm/20mm.
-length of planks not important as will be cut down to individual shelves of approx 34cm length.

I dont have a car so needs to be walking distance of East Worthing.

Thanks very much in advance :)