Heucheras come in several leaf colours and look good for most of the year.

Just a couple of ideas for you here, lamium yellow arkangel does really well can be invasive in a nice sought of way, lovely silvery/green foliage all year round and beautifull yellow flowers early to mid summer, another choice, is vinca green or varigated lovely blue flowers in the spring/early summer, very invasive, both euonymous green and yellow do well, let them scramble or clip them to keep them compact, incorporate some spring bulbs here and there, possibly avoid these if conifers are to be planted.

Thankyou for your ideas. I will have a look in my gardening book to see what the Lamium looks like as thats a new one on me. I do like the look of the Heucheras too & its not something i even considered.
Thankyou