Hi there,
Is the £1600 - £1800 / month figure inclusive or exclusive of bills, utilities, council tax ?
If exclusive, you'll need to budget at least a good £300+ per month for all these and possibly more - such as insurances.
If inclusive - then I'd estimate the range of properties you'll be looking at will be in the £1200-£1400 / month range - and around Heathrow/Slough/Iver, Windsor, Ascot, Egham and quite a few more areas/towns - you'll find something quite suitable for that price range. 4 bedrooms 'might' be pushing it a bit, but there'll probably be some room for negotiation etc.
There's quite a few threads about this kinda area, plenty of posters here live around here, including many movers like yourself. As the UK is so congested/compacted - you have many choices - also
how far out would you like to live from the job location? will you be commuting by public transport or your own car? Schools for the 5 year old will be a consideration etc etc
Some more info would be good
Cheers! DtM! West London & Slough UK!