steven - No.
Granted it will not be "valid" as a pilots license if you have not jumped through the required number of hoops within twenty four months of licence issue or last reavlidation/renewal - but it will not be lost either.
To "renew" your privileges (the term used when they have already expired) you will need to do a "proficiency check" - with an examiner. This includes a departure, two steep turns, two stalls, an engine failure from altitude, an engine failure after take-off, a normal (full flap) landing and a flapless landing.
(I wrote that list from memory - may have missed something - don't quote me on it).
The results of the above are written onto a form (known as an SPA/LPC - half of which is mailed to the CAA, half of which the examiner keeps.
There are no revalidation requirements for the night flying anymore - that's why it's called a "night qualification" and not a "night rating" - you just need one take off and landing, in the dark, in the 90 days previous to carrying a passenger at night. (The "night rating" required five take-offs and landings every 6 or 12 months [I've forgotten which]).
Whilst responding to your mail - don't forget that if the "ill health" to which you referred was your own, and it prevented you from flying for a period in excess of 20 days, then you should have informed the CAA and your medical certficate may be invalid.
(Edit: My posting of this message crossed with the other answer you just received - same thing).