@JennyJ and up lose flowers do look similar, too. But OP said there were berries ... i don't think spiraeas have them?
It is however pretty easy to check it if it's anything commercially available. A trip to a nursery with a decent brunch cutting and a photo of a full plant would probably solve this mystery
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It looks like something we call here a 'Nannyberry". It does have that elderflower feel to it. Could be it https://www.shootgardening.co.uk/plant/viburnum-lentago
(photo from wildflower site)
There's many varieties of it all over, but leaves on your photo seem very similar in shape and as glossy.
It has flowers that are tiny and which have a flat top.
The leaves are compound.
https://www.botanicaplantnursery.co.uk/sambucus-nigra-9193-p.html
See images below.
The one in this pic reminds me very much of the "bridal wreath" spiraea, Spiraea arguta.
Mystery plant cannot see leaves clearly .
It is however pretty easy to check it if it's anything commercially available. A trip to a nursery with a decent brunch cutting and a photo of a full plant would probably solve this mystery