The mercury might not be rising as much as we’d like in early May in the UK, but Mercury is certainly doing so. The closest planet to the Sun is in the evening sky right now, in the north-west just after sunset.
You’ll need a good clear sky and a low horizon to see it, and because the sky is still bright at that time you’ll have to search carefully. Just as you are about to give up you will probably spot it as a starlike point, and once you’ve seen it it becomes easier to find it again. Venus is also appearing in the evening sky in the same direction, and it’s brighter but even lower, so you may spot that as well, or instead.
Here’s a tip. If you have a phone app that shows the stars, and knows which way it’s pointing, this is the time to use it! It will show you exactly which direction to look in, and how high Mercury is above the horizon. But even then, it won’t be all that easy.
Mercury is at its farthest from the Sun on 17 May, so a few days on either side of that date is the best time to look. Actually the crescent Moon is very close to it on the 13th, so once you’ve spotted the Moon you should see Mercury above and to its right. Venus is below and to the right of the Moon. Around half an hour after sunset would be a good time. Much earlier than that and the sky is too bright. After the 17th Mercury gets lower night by night, but Venus is getting higher, and on the 28th the two planets will be very close together, with Mercury to the left of Venus and a lot fainter.
Here’s a view about 45 minutes after sunset on 9 May as shown by the free astronomy software Stellarium, which you can also download for your phone.