Long Term Freelance Art worker/Designer Required

We are looking for a couple of long term freelance designers/art-workers and 3D Exhibition stand designers with CAD experience. We are a boutique agency that produces tons of print work, such as brochures, books, hand-outs, promo items, e-shots, logo designs, brands re-freshness, ppts, signage, exhibition stands, CADs and 3D Stand design and asset creation. We are looking for around a 50 hour pcm support, with our busier periods being between Aug – Dec, to which the level of support is expected to increase and often require a quick sometimes same day turn around (but nothing unrealistic) we have work ready to go… so need someone to step in super quickly. We would ideally ask you to quote on a job by job basis, in 15 minute increments as some jobs only require a quick tweak sometimes. Making a note of the job and invoices us at the end of every month. We are a small friendly team and very quick payers.