I recommend caution...
First the one good point: a person did turn up to do the work, and he was pleasant and competent.
Now, the less good points:
1 He was told by picturehangingservice to arrive 90 minutes after the time we had booked him to arrive.
2 We said we needed him to bring all the necessary gear to hang the two pictures - he hadn't been told to bring any.
3 They demand a substantial upfront payment (which we paid) - this turned out to be their 'commission', because the independent tradesman then expects to be paid in full. (The sum of the two payments equalled the original quote, which meant that picturehangingservice had already paid themselves in full for a 'service' which they were yet to provide.)
4 We tried to phone picturehangingservice about 6 times to discuss this, but they did not answer their phone.
5 They claim to have 4.5 star review rating on Trustpilot, but this appears to be their first actual review.
Postscript: I did eventually manage to contact them through WhatsApp. They said that the 4.5 star rating was from their parent organisation (they didn't name this, so I can't verify), but did not answer my other points, despite repeated requests.