Apologies to those people who have been experiencing problems with either or both my site and forum being up one minute and down the next. Both have also been plagued by redirects to some spammy sites too. These issues have all been fixed now (fingers crossed) so life should return to normal once more.
For the curious amongst you, my provider had "DNS problems" with my site (and indeed many others) which meant, depending on where in the world you were located, you'd either be able to access my site/forum without issue or face the above problems. What made matters more irritating is as these DNS issues were propagated around the various name servers dotted around the planet the behaviour of my site and forum would change several times a day.
At the beginning of the year I decided to migrate my sites to a new hosting provider. I believed I was moving to a more robust one. It just goes to show the grass is not always greener on the other side
Thanks to everyone for their patience and also to those people who helped me build up a decent picture of exactly what you were seeing.