"Mel" wrote
My gardening books advise digging an allotment and adding manure and lime
in the autumn or winter. The books also say that manure mustn't be added
just before planting carrots and onions, and digging shouldn't be done
just before planting brassicas.

I didn't have any manure in the autumn but I do have some now. Is it too
late to dig, manure and lime now? I'll probably be sowing and planting in
a couple of weeks.

What we do is to divide our veg plot into 4 so we have a 4 year rotation.
In year one section 1 gets lots of manure and then is used for spuds,
section 2 is limed and used for brassicas, section 3 is used for peas and
beans* and section 4 is for onions and rootcrops*.
The next year sees it all move round one so that last years manured potato
plot is limed and used for brassicas etc.
Basically only a quarter of the plot is manured each year and only a quarter
is limed.
* we do chuck on some Chicken manure pellets on these years.

Having re-read that I do hope you can understand what I mean.

--
Regards
Bob H
17mls W. of London.UK