PPRuNe Radar, BEagle:
Depends how long ago your last certificate of experience lapsed. 4.5 years is one set of rules; over five years is another set of rules; over ten years is "training as necessary to pass the skills test" and then pass the entire skills test. Since my licence was last valid in 1990 that's what I have to do according to the documentation (and I have checked with the CAA).
At least the "training as necessary" is up to the discretion of my flying school, there's no minimum hours of anything in particular.