B&Q for the wood, local DIY store for the runner (less than £2 for 8ft, about £7 cheaper than online)
Dimensions are:
Each viv - 30" wide, 18" Deep, 18" high
Top middle rack - 30" x 18" x 9" with 3 x 9lts tubs - heated via strip
Top section - 3 x 10" compartments for bits and bobs, but im removing them to fit one large tub for another adult.