Jasmines tend to be vigorous - I'd be concerned that it might swamp your clematis. How about trying annual climbing plants - such as Cobaea scandens, Rhodochiton or Tropaeolum?

They do need full sun though.

Hi Spritzhenry, Thankyou for your comments and advice. where could I purchase these plants you recommend ? what do they look like,and can I plant them not?

..or something like Mina lobata, with lovely yellow/orange/red graded flowers from August onwards.

Tropaleum can be grown from seed,but must be grown every year, and I believe Cobea doesn't go through the winter either. Why not have a look at other non evergreen clematis, such as Lady Northcliffe, The President, Niobe.These are in the no prune group, and flower twice - first in around late May with large flowers, then again in July with smaller flowers. Or choose a late flowering one from the viticella group, such as Etoile Violette, Comtesse de Bouchaud - ones in this group, though, will need cutting down to 3 buds, or about 8 inches, from the ground in mid February, so you'd need to make sure you were cutting the right stems down, not the evergreen one by mistake!

That's why I wondered about annual climbers, Bamboo.

All the ones I suggested, plus Mina lobata, can be easily grown from seed - there's also Morning Glory, which would also give you flowers a-plenty - also an annual climber.