Where in London or UK wide can l get a second hand Lexus
IS 200 or 300 not too old ata decent price. I.e less than £18K.

Where also can l get an IS220 or IS250 to buy at a price that is approx or less than £22K

Try any lexus dealer, no doubt they get trade ins or used lexus's. A lot of business men drive lexus and usually upgrade on a yearly basis, best time to try is when a new reg comes out.
But if your looking for cheaper motors, better buy private than from a dealer, dealers will always charge book price..
hope this helps...

Avoid high price Lexus/Toyota dealerships, Look in Auto Trader, Small ads and head north. The further north you go the cheaper cars become.

l looked at 2 12 month old Audi A4's, Identical 2.0 FS l SE Spec, Identical in every spec, only colour and alloy is were different. 1st car came in at £21,275 in Surrey and the 2nd one just shy of £20k in Bolton. Both without haggle.

Auto trader

http://autotrader.co.uk/