i have a fenced square relatively flat lawn that is south facing, it gets the sun most of the day, however i have found that the lawn doesnt drain very well at all and even in the summer is quite damp and the back 40 % of the lawn is thick with moss. i have dug a few inches down and it does appear to be some clay present.

i have been advised to do several things including:
a 2ft by 2ft soakaway at the lowest point { not really an option as i have other gardens surrounding me and i fear affecting them as a result of this},

a herringbone drainage system to an existing drain :
either using a: garden liner based 4inch trenches filled with fine chipings
or b: circular porous drainage pipes in the above mentioned 4inch trenches { a costly possibillity},

and { the easiest option and possibly cheapest in my case } to rotivate in a couple of tonnes of sand, level the lawn and start again with seed or turf.

im really stumped as what best to do as i want to do it "right" first time and not have to be looking on here for answers this time next year again!

any advice would be great! cheers!