Due to fly to Bangkok on Thursday, should we cancel or should we just bite the bullet and go? Help from any-one already there would be massively appreciated!!

Suvarnabhumi Airport is where most tourists land at. That airport is high and dry. The airport was constructed to be higher than the surrounding area to prevent flooding.

As of right now the areas popular with tourists like Siam area and Sukhumvit are okay. Tourists are advised to not visit areas near the Chao Phraya River. Skytrain and Airport Rail service is still working. City Rail service in Bangkok are overhead and off the ground. Buses and taxis are running but avoiding any areas that are flooded.

The flooding is primarily in a lower section of Bangkok closer to the river and not the entire city. The flooding is mostly in Bangkok, other cities in Thailand are okay to visit. Some cities you may prefer to fly to; buses will go around any areas that are temporarily blocked. Tourists are still flying to Thailand by the thousands but many are going to other cities. Although many tourists do venture into Bangkok but stay clear of river areas unless they are going for a photo op.

I would not cancel but that is me. Lots of tourists including "little old ladies" are still showing up in Thailand right now but playing it by ear. Buses and taxis available at the airport for rides to Pattaya/Jomtien area or other areas in Thailand. You can take the Rail Link into the city and get a hotel near the Rail Link or switch to the Skytrain and get a hotel in Siam or Sukhumvit if necessary. But remain flexible.
UrbanRail.Net > Asia > Thailand > Bangkok Metro

Bangkok is serviced by 2 airports. Old Don Muang is on the other side of the city from Suvarnabhumi is closed. That airport serves the Thai Air Force and 2 small discount airlines. Only part of the airport is closed but no tourist flights from there - use Suvarnabhumi.

Flooding info:
UPDATED 30 October: Maps of Flood Risk Areas in Bangkok #ThaiFloodEng | Thai Travel News
Thailand Floods 2011 ? Google Crisis Response
Bangkok Post : Floods peak, defences hold
Bangkok flood latest news, Thai flood, Flood Map, Thailand news, Breaking news, Stock market - The Nation

I am back in my own country right now. But I get daily emails from friends and there are other sources to check on current flooding. When you get to the airport you will know where best to go. Usually Sukhumvit Road (low number end near Nana/Asok) has been pretty good for flooding even red and yellow protests and also with cheap hotels. Some minor flooding on the big number end of Sukhumvit when a barrier broke a little but only for a short while. Some hotels near the Ratchaprorop (Pratunam) Rail Link Station you can walk to.

Up to you. (Up to me I would not hesitate!)

Do you plan to stay in Bangkok or just land there to continue your trip to somewhere else in Thailand ?

Because if you don't stay in Bangkok, there is really no reason to cancel. The international airport works as normal. There will still be difficulties to go to the North of the country by bus or train ( no problem by plane ) but if you plan to head to the South, no need to cancel. it will be fine.