To answer this question, you have to look at what the RAF replaced it with. The Bulldog.
Except that it didn't replace it entirely. The Bulldog came along in the early 70s and replaced the Chippy in the University Air Clubs Squadrons but the Chippy was still being used for elementary flying training for direct entry pilots until 1993 and only left RAF service at the same time as it's replacement. I never hear anyone waxing lyrical over the Bulldog like they do the Chipmunk.
When the RAF EFTS was being closed down to be replaced by a civillian contractor, there were five contenders using four different aircraft - the T67, the SAH1, the FFA Bravo and the Zlin 242L. The EFTS instructors flew them all and we were unanimous that the Zlin was the best, but none were as good as the Chippy. In the end the T67 won based on the whole training package rather than the quality of the aircraft - and no one will ever convince me it was a worthy successor.
OK, so the Chiipy is costly, underpowered, doesn't carry enough fuel, expensive to run, slow, cold and prone to spin according to the posts here, but for pure flying pleasure and delight in handling, there is no better. No aircraft built since 1948 can match it.
So in my opinion, the question as to what can replace the Chipmunk can best be answered with "nothing".
