My opinion, I would say away from electric mower as a risk with wet grass or cutting the lead etc. People have been killed with electric mower or finger chopped off. Engine mower much safer and more powerful.
What shape is your garden? It's no good having a heavy pertol mower if you have lots of curves and beds to mow around, unless its a hover mover.
I would agree with masona, and stay away from the electric types. They are a bit limiting in that you have to wait for the grass to be almost dry, not much good in the early spring and autumn when there is a lot of dew about. If you do buy electric, make sure you have an RCD to protect yourself from electric shock should you inadvertantly run over the cable.
If you have a flat lawn and want stripes you would be best with a cylinder mower. If the ground is unven you will need a rotary mower, but stay away from a hover if its very even, they dont like big lumps and bumps. Check out the B&Q website, they frequently have good offers on lawn mowers
I've been using a Flymo hover mower for 20 years.
I changed the blade once but it came with plastic blades which you can use to keep the grass trimmed.
The plastic blades are very unlikely to cut through the cable unless yo are deliberately trying to do so.
As for uneven ground.
I've used it to cut the grass on the bank of the brook but made sure it didn't topple in.
I've seen hover mowers used on the end of ropes to cut a gras bank alongside a road.
The guy had 2 ropes attached and was sitting at the top using the ropes like reins to guide the mower from side to side.
By using 4 extension leads I've cut the grass for 20' either side of my garden end where a footpath kept getting overgrown from little use.
20 years for a £70 mower is good value for all I've put it through.