Should really get round to actually doing something with my Eldar Revenant Titan, have been meaning to paint it for ages now
That's pretty much what I've done. I find painting them really relaxing. All started off with the Space Crusade/Dungeon Quest games for me. So far I've collected a hodge podge of Dark Angel & Chaos Space Marines (was going for a "Fallen" DA army), Necron, Eldar/Dark Eldar & Nids. I just buy units that look interesting to paint. Someone my mum knows has just given her all her sons old boxed GW games for me including: 2 boxes of the Space Marine game (epic scale - 1 of which was unopened) 2 boxes of Blood Bowl (1 with the old card game board and 1 with the foam board) various expansion boxes and several boxes of painted and unpainted minitures for both the normal WH and 40k and Epic scale Titans. Although, I'll have to buy more paints now as the newer paints I bought have all dried up (the paint in the older style pots seem to last a lot longer than the newer screw cap style ones).
I recommend Vallejo paints, you can get them off eBay, they do equivalent colours to the citadel range called the game color range (they were rumoured to have been offered a contract to make the citadel paints, when that fell through the just released the range anyway). They're higher quality (although the citadel paints are certainly good paints, so this doesn't make a huge difference to me as I'm not that great at painting) but most importantly the bottles are much better. They have an eye drop style bottle, so you can drop a teeny tiny blob onto a palette or drop a huge amount, they don't dry out in the bottles at all and it makes it much easier to mix paints. Only problem is, because they have so much pigment they separate quite easily so require a lot of shaking, and they dry out on the palette quite quickly too, although I just damp my brush whenever they dry up a bit, a wet palette would be handy (you can buy them or you can make your own out of a damp sponge and some grease proof paper.
Oh yeah, here's a link to the seller I use, the prices for individual paints are a bit higher than what GW charges but the group buys are cheaper, I think they work out about £1.50 each. There's also an conversion chart here.