I have removed the AC Power connection from the main incoming cable and ran a new dedicated 2.5mm circuit from the consumer unit.  The only free breaker was a 10 amp and so far it hasn't tripped. Should i change it to a 20 amp?

What does the cable feed?

 

If the load is less than about 8A then leave the breaker as it is, no harm.

6 hours ago, Crossy said:

What does the cable feed?

 

The circuit has 2 sockets and the AC on it. The first socket has a floor fan. The other socket is in the car port and is rarely used. The AC is a Mitsubishi inverter rated at 6.8 amps. I guess the 10 amp breaker is adequate. Thanks.

2 hours ago, stubuzz said:

The circuit has 2 sockets and the AC on it. The first socket has a floor fan. The other socket is in the car port and is rarely used. The AC is a Mitsubishi inverter rated at 6.8 amps. I guess the 10 amp breaker is adequate. Thanks.

A breaker is there to protect the cable, for that job you can use the rated size or anything less, if the small breaker does not trip there is no need to change it.
 

FWIW the AC rated at 6.8 amps is unlikely to use more than 4 amps for most of the time.

Also the breaker is likely to not trip until you are using over 12 amps for a reasonable period ½ hour and over