I need to replace a couple of table lamp light bulbs so need the equivalent of the old 40 watt bulbs - but I can't make head nor tail of the new bulb wattages - what do I need to look for?
As O_G suggests, you should be forgetting about Watts (after an initial conversion in order to give you a reference point) and thinking in terms of Lumens.
Buenchico is right but you also need to think about light temperature...the actual colour of the emitted light. Yellow light ie warmer and cosier, white light may be better for working but can be cold and casts harsher shadows.
https://www.thelightbulb.co.uk/resources/colour_temperature/
>>> you also need to think about light temperature
Agreed. That's measured in Kelvin and you should see it shown on the side of the box. Fortunately though there's usually a graphic to go with it, which tends to make things a lot clearer without having to bother too much about numbers!