Well, not giant, or mutant. But chilean tarantulas. and they could take over the country!
Or not, chances are they cannot survive in the UK climate... unless they MUTATE!
Chilean tarantulas menace Bolton
The RSPCA has warned the good burghers of Bolton to keep a sharp eye out for Chilean Rose tarantulas after a couple of the eight-legged critters were spotted in local gardens.
The organisation reckons the two may be from a larger batch of arachnid escapees and, if the Telegraph's headline is to be believed, it could be just a matter of weeks before the entire country is blanketed in a seething mass of alien spiders.
Read more @ The Register

ok...first in my head, throughout reading this article i was imagining octopuses... Secondly, i thought i was going to have a heart attack for so many reasons when i clicked the link.
Octopuses are so much easier to spot then spiders...
euh...
Whjat would be more dangerous... a mutant crossover between giant tarantulas and octopuses, or a crossover between months and pirhanas?
You can only be young once, but you can be immature for life.
the thing is, you wouldnt often see a taranopus. whereas a mothanas, THAT you'd see often...
euh...
Did you hear about the donkey who has zebra legs?
and if you find a four leaved clover, just get excited. It's a mutated clover
I'm fly.