Occasionally, and particularly at this time of year, you will find special offers of petrol lawn mowers from about 150 to 190 in Woodies, Lidl, Aldi, or even some Dunnes now. Most are pretty good quality, and, if maintained well, will last several years, depending on the amount of use. Woodies currently have a 40cm Petrol Rotary on their website fro 149.99.
I am no expert, but here are a few things to look out for:
get a four stroke (most are four stroke nowadays)
A rotary mower is more flexible than a cylinder mower. A cylinder mower will give you pretty lines, but the grass has to be almost dry, whereas you can cut damp grass with a rotary;
Try to get one with a Brigs & Stratton engine, which I have always found to be reliable.
With a .66 Acre garden, you will probably want to get a self-propelled, but that will cost more.