PTPHs are purely formalities when the defendant pleads not guilty.
He/she is asked to enter a plea and, when the response is 'Not guilty', the judge has to decide when the trial will take place. In order to do so he usually confers with the prosecution counsel (to find out when the CPS will be ready to take the case to trial), the defence counsel (to check that the defence with have their case ready in time) and, probably most importantly, the court official who books the court rooms and checks that there's a judge available for any relevant dates.
A defendant has the right to bail unless the prosecution can show the court that there are one or more reasons why it should be refused (such as a likelihood that the defendant will abscond or interfere with witnesses). If bail was granted by magistrates when the case was sent to the Crown court it's extremely unlikely that it would then be refused by the Crown court but if, say, the police or the CPS had become aware of the defendant making approaches to witnesses, it might then be refused.