gathered my thoughts a little better (low end laptops are quite a minefield to pick out decent value). looking for a family laptop mainly for the kids. homework plus basic gaming - primarily minecraft. Keeping it below £500 would be ideal.
Thinking that a 4200M and 4200U should both be enough power for general use, but the 4200U should be with dedicated graphics as otherwise it gets clocked down due to the limited TDP. 4200M should have a faster IGP and be able to use it better due to the higher TDP of that chip.
options (in order of price):
1) Lenovo G510 £429
i5-4200M
Integrated graphics (but being the 4200m this shoudl be the HD4600 which should be ok for basic gaming?)
4GB RAM (can upgrade myself)
15" 1366x768
notes: slightly faster CPU than the 4200U and acceptable GPU?
2) Lenovo Z510 £499
link
i5-4200M
GT740m 1GB (says DDR3 for GPU ram though. eww)
4GB ram (easily upgraded)
15" 1366x768
3) Lenovo G510 £537
i7-4700MQ
Integrated graphics (should be the HD4600 which should be ok for basic gaming?)
8GB RAM (can upgrade myself)
15" 1366x768
notes: fastest CPU and acceptable GPU but worth £100 over the i5 4200m?