My ultra reliable 2001 2.0 Zetec Focus has had her first fit!

The other day I got some NGK plugs and gaped them at 1mm, car ran better than when I had the Super 4's in so all good there. I then decided to clean the throttle body. I got the throttle body off and gave it a major clean as the back off the flap was coated in black grime. No de-greaser worked so I used fine wet sandpaper and rubbed it off. Put it all back together, started it and all was good. Today I went down the road and noticed as I dipped the clutch the revs went up, then when I came to a standstill the revs would hold at 1,600 for a few seconds then drop to normal being around 900. This got worse as my journey went on, as I pulled into the petrol station the revs were 2,000 and stayed there for 5-6 seconds before dropping to 900. Any ideas on this? Also I dont know if this could be related to the above problem but my speedo sometimes stops working for a minute or so then comes back to life.....although this did not happen today with the high idle.

Any help would be great as she will be using heap loads of fuel and at £1.36 a litre my wallet will soon be empty!

Thanks in advance.