ok, before i had a bath, i sprayed liberal amounts of wd 40 around the base of the seatpost. then when i went back to it scraped the rust from around the seat tube, used a screwdriver to prise apart the clamp, then after about 2 mins of twisting the seatpost, with a little help from the wife off it came, to say i'm ecstatic is an understatement.
i kind of had a feeling i could get the seatpost out.
i thought the bike would be massive, but from crank centre to top of seat tube its 19", just perfect for me.