The Natural Philosopher wrote:
[snip]

we hae an itinerant hairdresser. Very fast very cheap. She is self
employed, but the scope for offsetting every single thing, all the car,
or most of it, all the tools, even a set of working
clothes..phonecalls..even before a few quid a week may or may not slip
into the purse for the tescos shop.

That's complete and utter ******** as you would know had you ever run your
own business. You cannot "offset" every single thing and the rules relating
to cars are complex and require the maintenance of a log if the car is used
for mixed personal/business purposes. Much of the expense related to
running a car cannot be offset against tax.

A set of working clothes hardly amounts to much and only a few trades,
including lawyers can claim for working clothes. Tools yes of course why
should one not be able to offset tax against these? Note that if at end of
life any of these items are sold then VAT, income tax and possibly CGT must
be paid on the sale value.

The picture you are painting of the self employed on the fiddle is a
fantasy. Ask Dave TMH for example.