FLASHING INTRUCTIONS:
The one critical step to a successful flash is to set the host computer to a static IP in the range matching the router- 192.168.11.x (x can be anything between 2 and 254).
My computer wired to the router is set on a manual IP, im taking manual means static, as the others I haven't set still say auto. The IP is 192.168.11.X, x being the number i've gave it.
Set the pc IP to 192.168.11.1, browse to your intended .bin (firmware) file and select it, leave the password blank and set the retries to 99 (20 is usually enough).
This bit has got me abit lost, I thought the IP of the wired computer should be as point 1? Sorry but i've never done this before so pls go easy. Or do you mean change this on the PC and not the router?
Make sure your ethernet cable is connected to the NIC on the computer, and a LAN port on the router.
Im guessing here but should I only have the host computer connected to the router and nothing else? Take out the cables running to my PS3 and take out the cable from my modem to my router (or will the modem need to be connected). I always have the router connected to my main PC but would the cable need to be in a different port?
Click "Upgrade" on the tftp utility, and casually put power to the router. The utility will attempt upgrades and fail.....that's fine. Watch the LAN icon in your task bar as it attempts to acquire an IP. Just as you see it connect and find an IP, the utility will begin to flash the upgrade to the router. After it's complete, sit and wait about 2 minutes (more or less, depending on variables) and the router will reboot itself. When it's finished booting, it's done.
This bit sounds ok, except for casually add power? Please can you explain abit more.
Reset your host computer to its previous IP configuration. This has to be either DHCP or static in the range of 192.168.1.x., because now that the router has DD-WRT flashed, it's IP has changed from 192.168.11.1 to 192.168.1.1. Do a hard reset on the router and it's ready to configure.
This bit, im all confused 
. Sorry mate but these instructions are sending me dizzy. I think I might be out of my league here. I think I need a flashing guide to a complete DIVVY. Im confused with keep changing the IP address.
This above method is easy and i've done it a few times on the same router, MY DDWRT is v2.3 sp2 and does not include the latest ddwrt which has a more features on it.
If you can be assed going through my points i'd be mucho grateful but if you can't be bothered and think this is a to big a job for me, NO problem sir. I know i've asked alot but thanks for the information you've given me so far.
Hope that's helpful.