Microchipped cat flaps

Marmaduke123

Our rescue cat had no problem adapting to a microchip cat flap. He didn't seem bothered by the clicking, he just wanted to get in or out!
We had to use treats to get him to stick his head far enough in to programme the cat flap before installation though.
The new cat flap needed a hole which was slightly smaller than the existing one, so a bit of bodging was necessary.
You know your cat, but I  personally think
the constant on going stress of another cat coming in would be far worse than a short period of getting used to the slight clicking.

jenny-wren

Another vote for Sureflap.  We have the Surefalp microchip pet door (our cat, sadly no longer with us, was rather chubby and wouldn't fit through a normal sized flap!).  Ours is installed in glass French doors and we had a few issues with getting it to work at first (I believe that some metals in close proximity to the flap can cause problems).  Sureflap were amazing and ended up sending us another flap which worked fine.  Their customer service is second to none.  You can change the delay time (the time it takes for the flap to lock) and set curfew times (once the cat comes in it can't get out again until the time set for the flap to open).

No other cats managed to force their way in (believe me, many of them tried).  The Amazon delivery driver managed to deliver a parcel through it one day, presumably the cat opened it for him!!!

Brambling

Having carried a complaining cat out of the house twice before 8am this morning I shall be investing in a Sureflap, I'll just need to check the measurement of the existing hole to confirm I don't need a new door panel.  It's good to know i can set curfew times as well. 

Thanks for all the advice, I just have prepare my cat for change and he's a creature of habit 

YBR

Interim measure: try lemon juice (or other citrus).
Cats can't stand the smell so if you dose the kitten with lemon juice (a few drops on the fur) when it comes it it should be a harmless deterrent.
We once got close enough to spray a bully-cat in our garden with a jiff lemon and then didn't see it back for over a year! 
Sample of one, but not expensive or difficult to try.