Again, CAP413 1.2.1.g - Transmitting Technique - Avoid using hesitation sounds such as "er".
Of course that's the official, and sound advice. But there is a subtle difference between:
"Tower, G-CD request"
and
"Er, Tower, G-CD question?"
In the first case tower knows I have a rather lengthy, but CAP413 compliant request I. In the second case, tower knows that something non-standard is going to happen. This might influence his decision on whether to let me go ahead straight away, or put me on standby for a few seconds so that he can issue a few landing clearances first.
In a busy environment, stick to CAP413. But if it's quiet on the frequency you can sometimes get away with subtle or not so subtle deviations from CAP413. "Good morning", "bye bye" and "thank you" are the most common deviations and I don't mind an "Er, standby" from the tower too if I've just asked an unusual/unexpected question and the tower needs to think about how to handle that. At the end of the day, we're only human!
On the other hand, if I've just called "short final" and the tower responds with "Er, standby" I might not be too happy about it.