there great as long as you sevice it once a year, if you can't afford it, do it yourself, clean the plug every few months and change the oil blow out the air filter, job done, get one with a bag to catch the cuttings, when your cutting the grass if it starts to leave cuttings behind you the bag is full, if your grass is very long set the mower to the highest setting then do it again with the settings lower, the height settings will be on the wheels very easy, buy one that uses straight unleaded petrol not 2 stroke (which means you need to mix special oil into the petrol)
Having worked in the horticultural industry for over 30 years it is far better to use a good petrol one rather than an electric.
Saying that it does depend very much on the size of your lawn , how much you cut it and what type of finish you expect.
Therefore if you have a small lawn and want it always looking good then an electric flymo will be best. It much quicker to set up and maintain. However if you have a large lawn the petrol I'd by far the better option for both speed and quality.
I got a petrol mower from lidl a few years ago with a 3 year warranty was £200 I think, briggs and Stratton engine also self propelled (unless you don't mind pushing), not sure if they have just had a petrol mower for sale!
One more point about maintenance is that you should always drain the petrol from them when you lay the mower up for the winter, as fuel left in the mower over winter can cause problems starting in the new year.
Ive had a Mountfield for about 6 years, all Ive done is top up the petrol and its going on like a work horse.
On a separate note (and it was that, that led me here) does anyone know if I can use 5w30 oil on a petrol lawn mower? Ive been googling and notice the stuff to buy is SAE30 but I also noted people saying you could use 5w30 - any ideas?
On a side, side note - just noticed on B&Q you have to be over 21 to buy a petrol lawn mower, is that in case you try and drive the thing home?!! (Guessing most people 21+ would have their driving license) but how ridiculous