One idea might be to get yourself a keysafe, which is basically a small box fitted to the outside of your home and specially designed for a holding spare key. The key(s) can only be accessed by those knowing the combination. Here's an example of what they look like:-
Once the home help has the key out of the safe they could still take it away and have another one cut. If the home help has access to the house surely if they are up to mischief not having a key makes no difference.
I believe that many local council property keys are stamped on the key grip �Do Not Copy�, or some such similar wording (this avoids them having to replace locks, each time a tenant is moved).
In order to get a copy, you would then have to take it to an unscrupulous key-cutter.
i wouldn't under any circumstances let your home-help have your key. my ex cleaner (of 5 years) said she'd 'lost' my front door key when i asked for it back when our business relationship ended. it also had our alarm key on the key ring. after numerous letters to her (she wouldn't answer her phone), we finally just changed the lock and have since had a key-less alarm system fitted. my advice is definately don't do it, you have to be very, very cautious who you lend/give a key to.
There are many restricted key systems made for different levels of security. Contact a local independant locksmith from MLA or ICL. What area are you in?
The best are patented which can give up to 20 years protection. Some have moveable elements in the key which makes producing a copy blank more trouble than it's worth.
Others have a registration card and rely more on the honesty of keycutters, just how dodgy is the home help and friends?
Abloy protec or exec. Dom ix10. Assa Twin Combi. Chubb RKS. Banham dimple. Multilock MT5 or Interactive. Medeco. Evva MCS. Winkhaus VS6 etc etc