This is your own thread, called "roof rails" which I made for you when I saw you'd posted into the end of another thread. This will be post 5, and don't worry, we were all new once and none of us are getting younger
A thread is usually about a single subject, and can have as many posts in it as you want, every time someone replies (or you do) it adds another "post" to the "thread" so keeping all replies under one roof so to speak, about a person's question. You can also post as many new "threads" as you need to, on different questions, in the right forum section. Your car is a B9 so you'd want to mostly post questions (threads) in that area. But this is your thread so post anything you want to know in this one if it's easier!
So, the timing belt on your Berlingo (assuming it's the 1.6 HDi diesel) needs to be done at 150k miles, or 10 years which ever comes sooner by Citroen's reckoning. Can be done before that, I'd say up to 100k is sensible but at 35k it's hardly turned a wheel so you wouldn't need a cambelt on mileage and it's not 10 yet, so maybe worth a reputable garage checking the condition of it at the next service. If it shows no signs of fraying or chipping and the tensioner isn't siezed, it wouldn't need changed but take the advice of a mechanic you actually trust....cos it's not cheap, but the results can be bad if it goes.
On my opinion, you'd get at least another 2 years before it hits 10 years old. Then I'd do it.
Mine is on 64k miles, and is 10 next year, so if I've still got it by then I'd be thinking that way too.