I was at the Interiors UK show at the NEC today and saw an adjustable height dining table made by Skovby from Denmark. It looks great and costs around £2600. It is worth considering if you are worried about the effect that working at the dining table is having on your posture.
Another alternative could be the Swedstyle adjustable height table frames - these can take tops up to 2.4m long and 1m wide and can be adjusted for standing and sitting at any height. These will also take pretty much any type of table top. Recently a customer of mine had a top specially made from recycled scaffold boards - it looks fantastic and is eco friendly. The whole thing cost him around £1550.
The Swedstyle frame is the top image and the Skovby table is the bottom one.