Mary May

I don't know much about this author. She has written quite a few pony books, some forming a series about a girl called Carol, some stand alone stories and a couple books of short stories. The books are I think all self-published and there appears to be no trace of the publishing company (Manor Acre) on the internet so I assume it is not trading as a business any longer.

The books are fairly unusual in theme. Many of the stories centre around driving, an equestrian discipline which is not popular in pony books. Also the main character of her Carol series is a disabled girl, another rarity for a pony story.

Popular illustrator Anne Graham Johnstone illustrated many of the books. (She was most famous as half of a partnership with her sister Janet, and together they illustrated a number of children's books including the
Faraway Tree series by Enid Blyton and some of Lorna Hill's ballet books.)

Carol Series:
Unusual pony series about a girl who can no longer ride after becoming disabled but continues her passion for ponies when she learns to drive them instead.

1) THE WILL TO WIN
(MANOR ACRE 1993)
ILLUSTRATED BY ANNE GRAHAM JOHNSTONE

2) PIEBALD IS LUCKY
(MANOR ACRE 1995)
ILLUSTRATED BY ANNE GRAHAM JOHNSTONE

3) DEEP WATER AT DEREEN
(MANOR ACRE 1996)
ILLUSTRATED BY ANNE GRAHAM JOHNSTONE

4) ONE FOR SILVER, TWO FOR GOLD
(MANOR ACRE 1998)
ILLUSTRATED BY ANNE GRAHAM JOHNSTONE

Collectors Info:
All paperback originals. Most of them can be found reasonably easily in the UK. The first in the series, Will to Win is a little harder than the others. All of them are quite hard to find outside of the UK. 

Other Horse & Pony Books:

A PATCHWORK OF PONIES
(MANOR ACRE 1997)
ILLUSTRATED BY ANNE GRAHAM JOHNSTONE
SUMMARY: Short stories.

A PARADE OF PONIES
(MANOR ACRE 1999)
ILLUSTRATED BY SUE SCOTT
SUMMARY: Short stories

DEFIANCE AT THE INN
((MANOR ACRE 2001)
ILLUSTRATED BY SUE SCOTT
SUMMARY: Historical pony novel

THE HORSE OF DREAMS
(MANOR ACRE 2003)
ILLUSTRATED BY GREG LARCOMBE
SUMMARY: Younger readers picture/colouring book about a rocking horse

A POCKETFUL OF SILVER
((MANOR ACRE 2005)
ILLUSTRATED BY SUE SCOTT
SUMMARY: Historical pony novel

Collectors Info:
All paperback originals. One for Silver and Defiance at the Inn are, if not common titles, not too hard to find in the UK. The others are hard or very hard to track down.