I have some MK grid dimmer units which have failed, and they look to be over £20 each to replace. There are some Varilight "Uni"-grid dimmer switches at about £6 each, but I need to know whether they'd fit the existing patresses and grid plates that the MK are fitted in. E,g. MK Grid Dimmer Varilight Dimmer Will it fit or do I need to think about replacing mounting plates as well? Thanks.