It does depend which wylex boards you are talking about , 3036 rewireable fused boards still comply with the regs , how ever work requiring RCD protection will require an aditional board ,as RCD's dont fit the old boards and you cannot install an RCD to cover the whole board , also some of the wylex boards the early ones have a wooden frame at the back which can be a fire hazard if the board developes a fault within the board , this is quite common , another no no is with the wylex boards if you install minature MCB's in the board and the fuse cover is not adjusted to fit then you are exposing live parts so care should be taken , i always recommend that a customer upgrades to a new board mainly for added protection and easy of resetting tripped mcb's compaired to rewiring a fuse