One other thing You might have done but worth a mention. Is there a top point vent tube from the RH top side of the radiator running back to swirl tank ? Not sure when they brought this change in. The earlier cars did not have it.
If your still using it it would have been connected with a banjo fitting on the upper RHS of the original radiator.
The steel connection tube under the car will be totally absolutely and permanently blocked with crud. I replaced mine with 6mm 316 stainless.
Now it works.