MANCHESTER, England, Feb 13 (Reuters) - Giraffe Flowers in Manchester, northern England, is preparing for the annual Valentine's Day rush but florists fear that Brexit trade barriers will increasingly spell higher costs and delays for their business.

The company operates two shops in the centre of the northern English city and expects to sell some 7,000 roses in time for Valentine's Day on Wednesday.

Today Giraffe sells a bouquet of red roses for 40 pounds ($50.5), but by next year it expects that will cost 50 pounds - because of the phased introduction of post-Brexit customs changes on goods coming from Europe, which have already begun.

Since Jan. 31, traders of some animal and plant products, such as chilled and frozen meat, eggs, cheese and certain cut flowers, have been required to present Export Health Certificates (EHCs) to British authorities.

The regulatory burden is set to increase further. Physical checks will start on April 30 followed by a requirement for safety and security certificates from Oct. 31.

Anna Molicka, head florist at Giraffe Flowers, said she expected flower prices to rise by up to 20%.

"I don't think the borders are ready for it - maybe two days of delays because of that. It will affect the quality of the flowers... they will not come to us as fresh as they always do," she said.

The Dutch flower export industry has objected to the introduction of border checks and UK companies are concerned, but the British government says it is working to ensure the introduction of checks goes smoothly.

Britain has previously postponed full implementation of its post-Brexit border controls on food and fresh products five times since leaving the EU's Single Market in 2021, due to worries about port disruption and the cost-of-living crisis.

By contrast, the EU immediately enforced its rules, leading to port delays in 2021 and prompting some British exporters -- such as cheese-makers and high-end beef farmers -- to stop selling to the bloc, at least initially.

Molicka from Giraffe Flowers lamented the fact that customs red tape was on the rise.

"For the last 30 years there was no need for that... It all worked," she said.

Asked about the prospects for Valentine's Day sales in a year's time, Molicka said: "the customers will just buy less." ($1 = 0.7929 pounds) (Reporting by Phil Noble, Writing by Andy Bruce Editing by Keith Weir)