spiders or spider mite?

[The Mouse]

Help!
Went to check on my tomato and pepper plants in my polythene-covered greenhouse this morning and found strange 'clusters' that I couldn't identify straight away, near the top of two plants. It was only when I reached out to remove these strange things that it became obvious that it was animal (or rather insect), not plant. Each cluster divided into hundreds of tiny spiders, swinging around on tiny threads in a bid to escape!
My first thought was spider mite, but I've been searching the Net and none of the many sites devoted to these pests mentions them forming such visible clusters. Nor is there any sign - yet - of damage to the plants.
I've tried to have a good look at one, but they move too quickly!
I've removed as many as possible, but not knowing for sure what they are, don't know how far to go.
Any ideas? (Sorry, I don't have a digital camara, or I would have posted a picture.)

[Johnboy]

Hi Caz,
I do not think that you have any reason to worry.
You cannot see red spider mite with the naked eye and what I think you have are what I call money spiders so be respectful and buy a lottery ticket for the European lottery tonight.
JB.

[oldherbaceous]

Dear Caz, i agree with Johnboy, spiders and not spider mite.

Good luck with your lottery ticket.

[The Mouse]

Phew,that's a relief!
So do I let them stay? Do they make good (green-)house guests or not?

[alan refail]

Caz

I suspect they looked something like this

You touch them and they all descend quickly on silks, then, after a while, climb up into a bundle again.

Let them stay, please.

[The Mouse]

Yes, Alan, they looked exactly like that.
Ok, any that escaped eviction yesterday can stay. The rest were only removed as far as my nearest flower bed - I couldn't decide if they were a pest or not so opted for the soft option of giving them a new home!