In terms of pot time it looks fine but it doesn't mention anything about the viscosity of the mix. My guess is that the viscosity would be ok but do you really want to risk it for about £20? We know from others experience that West System is almost like water when mixed and will self level in the time it takes to set. Last thing you want is to mix up a big batch of this stuff, pour it on and then watch at it slowly sets with a dirty great lump where you poured it in. Other than that I'd say go for it, I'd certainly be very interested to see if there was a cheaper alternative.

As a side note, if you don't have them a cheap set of scales is well worth it, the density of the two components is different enough that by volume measurements won't cut it (unless you are going to do the calculation to figure out the correct volumes of course).