Does anyone know if there are lava tubes on Gran Canaria that I could easily visit when I'm there? Any info would be great, please!

Hi,
You may be out of luck on Gran Canaria as I don't believe there are any tubes there.
The main islands for tubes are Lanzarote, Tenerife and I think La Palma.
Ed may know better but I'm not aware of any there.

And,

I've not caved on Gran Canaria, but I do know that there are some caves.  The best starting point would be to have a look at the catalogue of caves on Gran Canaria in Vulcania (The Canaries caving magazine) No.9, which is available online here; http://www.vulcania.org/revistas/Vulcania_9/Vulcania9_pp43-47.pdf

According to this the longest cave is Cueva de los Arrependitos which is a whopping 201m in length.  I also believe that some of the other listed cavities are vertical lava vents / fissures rather than lava tubes, these would require serious tackle and care to  descend safely.

If you do manage to get to have a look at a cave or two whilst you are there, it would be really great to hear what they are like and see a photo or two on here.

There are some fascinating Guanche carved caves on the island near the centre - well worth a visit.

Thanks for the info everyone. I didn't think there seemed to be a huge amount in the way of lava tubes after a Google search (in English).
The caves sound interesting though, and hopefully I'll be able to check them out. 200m long is a Sidcot Swallet, so not to be sniffed at!