For £20 I reckon you can do what you want! Don't wet the grilles but maybe an upholstery cleaner?

rgs218:

Only thing is they're a little bit grubby in places - is there any way of giving them a light clean without damaging them?

If you can't get them presentable without using any detergent/water, check out what I did to my RL6000's a little while ago:

http://forum.beoworld.org/forums/t/24303.aspx

I believe the RL140's won't be that much different; just be very careful with the woofers. If they don't have foam rot already, they will at least be fragile... or if you're very lucky, fixed already - but I wouldn't expect that for the price you paid for them!