Alternatively (or additionally), if the play park was in the plans for the estate (whether approved or not) when the developer sold you the property, you would theoretically have a claim against the developer (and/or the developer's agent) for misrepresentation. However, unless you've got some paperwork showing that there would be no play park, it would be very hard to prove what was said to you.
If the plans for the play park were submitted and approved after you purchased the property, you won't have a leg to stand on unless you can prove that the council did not meet their statutory duties by placing notices in the local press, displaying a summary of the application at (or near to) the proposed site of the play park and giving due consideration to any objections. (If you could show 'abuse of process' you would need to contact the relevant ombudsman)
I've tried to indicate the three possible routes for complainng about (and hopefully resolving) this problem but, if I'm honest, I doubt that you'll be able to establish any sort of improper conduct by either your solicitor or the local authority.
I suspect that the 'blame' lies with whoever sold you the house but, as I've stated, unless you've got some paperwork to back up your statement that you were told untruths, you may find it difficult to seek redress.
All the same, I'm still certain that the local planning department should be your first port of call. Once you've established the relevant dates, you'll be in a better position to assess your position.
Chris