I think so, what is the existing cylinder like (factory insulated or not, quick recovery)? If replacing an older, un-insulated cylinder I would want to use a factory insulated model in its place.
Also all pipework connected to the cylinder should now be insulated- this should only add a few euro to the cost of the job and it's something you can do yourself. While you have a plumber in the house it is very worthwhile to have gate valves fitted on the feeds from your cold water storage tank in the attic- this makes future maintenance of your system very easy and avoids the need for drain-down.