If you are actually in the UK, I assume you're growing this plant in a warm greenhouse or indoors. Can you take a photograph of the beetle and add it to your question - it might be one that's migrated to this country on your plant rather than being any native beastie.

There are about 20.000 different beetles in Europe and 4,000 of them live in Britain. Lots of them are quite big so yes, a photo is pretty important if you can manage it.

If you cannot provide a photo I will ask you this - Do these beetles have antennae as long or longer than their body and are these beetles black with white spots on their body? As far as the cobwebs, get a magnifier and check for spider mites. Also, check the trunk of your tree for holes, these would be the exit holes for these beetles when they reached the adult stage inside the tree and bored through the wood to exit to the outside. Ok, I'll let it out. You may have an infestation of the Citrus Longhorned Beetle a big problem in the US right now just want to rule out a beginning problem in the UK.

Oh please no, Loosestrife, but it is a worry and that's why I asked for a pic - I'm hoping the asker isn't actually in the UK....

The beetle was found where you are in Essex in 2008. It got to the USA in wooden shipping pallets. The questioner is from the UK. V: you can answer us by just adding a comment to your question such as we are doing. You would be doing a great service to all if you do answer. Thank You. P.S if you have your plant growing in a conservatory go over every square foot of it and collect the beetles that you find and place them in a jar about half full with cooking oil. Keep on doing this as often as you can.