Colin Wilson wrote:

Any ideas whether lime mortar is suitable for repointing a cemented wall ?

You can use it but it isn't as likely to stay in place.

The colour of the sand used in cement mortar controls the colour of the
mortar and the strength of the mix controls the damage it is likely to
do.

If using soft bricks you would use an eight to one mix -which at the
price given in the OP (and the quantities of lime needed as three to
one) makes it a far cheaper alternative. It is with the overall concern
of the project and the consumer's tastes that the costs may seem small.

It isn't in the same category for example as the price of a new car
compared to a three year old one. You can of course use any inert
admixture to either sand or cement to make mortar. And you can get a
pleasant effect with different sands if shortly after the bricks are
pointed, the wall is washed.

Maching it all the way through the different courses would require some
skill though. Too many would-be bricklayers can't even put a wall up
without a great variety of shade in the allegedly same mix.

Errors to watch out for are bricks laid upside down and the poor
selection of bricks by the labourer. Each course must be laid with a
few bricks from each pallet to prevent the differences in batches
showing up.

Also a load of bricks should never be tipped out of a lorry. This isn't
so much a problem these days with most lorries transporting them having
grabs.

Too frequently the developer will not have all the bricks for an house
delivered on site in one or two loads. Often this is a space or
security limitation.

And these days most labourers have little or no training, with
bricklayers on pricework not caring nor being paid to point out tips in
such craftsmanship.