It wasn't the RAF, but I emailed the Royal Navy Recruitment Office based in London and they told me that you only go on deployment following the completion of your training at Britannia Naval College (for the RAF I assume it's RAF Cranwell), which is after the foundation years.
This is per the RAF Recruitment Office:
"As it states on the role page on the RAF Recruitment website, once you've completed all of your training then you could be posted anywhere the RAF has a station, this could be anywhere in the UK or around the world. You're posted every 2-4 years, so you'll move stations and jobs each time.
However, if you're talking about deployments then that will be wherever the RAF needs you to go (or the MOD, you can work alongside your Army and Navy colleagues too) anywhere in the world. You'll be advised beforehand, but you're not going to know now. Deployment is different to posting. Posting is 2-4 years, deployment will be for up to 4-6 months."
I'd assume that deployment for the RAF is less common in comparison to the Royal Navy.