I have a 53-39 set up on the front but there are too many hills around here!! Can I just swap the rings for smaller ones and adjust the front mech to suit? Thanks in advance.

Will

If that's how your chainset was supplied, then there's more than a strong probability that your chainset is either 110 or 130. Which in turn means the smallest inner you'll get is a 38T. The smallest outer would be a 46T, but you have to specify a 46T OUTER.
Have you looked at your cassette?

Depending on what spec your chainset is, you might find a whole new compact chainset going cheaper than rings alone.

I just bought a back up FSA Gossamer compact for cyclocross and it only cost £29. A new ring is about £26.

Cheers oldgit. Can I just put a full new crank on then? The one I have has had little use so could just sell that to offset the cost.

Yes as long as it matches your bottom bracket, what have you got?

If it woulds fit, I have a 36 inner ring on the classifieds…..

http://www.singletrackworld.com/forum/topic/fsa-36t-ring-as-new

surely just change your rear cassette?
Then you have a one for the hills and one for the flats?
Forgive the heresy here but hey even fit a mtb one?

cassette options are going to be limited by what rear mech is on bike

Again without knowing what will has, it's more likely he has a rear mech limited to about 27T if he has a bike supplied with a 53/39 chainset.

The crankset is a Ultegra SL

Smallest inner ring you can fit is 38t. If you want lower gears then sell the chainset and buy a compact double or even a triple if your shifter is compatible.

If you have Ultegra SL you don't really want to downgrade to a cheaper Shimano compact. Assuming it uses HT11 bearings, the cheapest compact would be something like a Tiagra at about £40.
I'd probably sell and replace it with the same spec kit.

Or move 😉

Cheers everyone. Oldgit thanks for the help. I will get a replacement SL one. It is a HT2 BB. Anyone want to buy a 53-39 crankset??????

53/39 is too Grrrrr for STW.

HaHa. It's no good for my old unfit legs!!