Before buying a spindle are you sure the gantry and in particular the Z-axis is strong enough because these Suregrave machines were built for engraving not cutting?

Both the 1.5 and 2.2Kw spindles are much heavier and longer than the engraving spindle and DC motor that would have been originally fitted, in particular, the length which will act as a long lever and if I recall the gantry uses a narrow rail system which doesn't offer much support for the Z-axis. If the backplate isn't supported well enough or strong enough or any part of the Z-axis is weak it will cause vibrations at the tool which will result in broken tools and a poor finish. Having a heavy and long spindle will exaggerate and quickly show up a weak Z-axis.