There is currently no microarray service provider in the UK that uploads your plant science microarray data to GEO on your behalf, but publication requires your data to be shared. The most common request from journals is that it is shared on GEO.
GEO has this information page about data submission. While the high-throughput sequence submission guidelines are a still little complicated, microarray experiments have well-established (and enforced!) minimum information requirements and the four main microarray chip providers have customized information pages. An email address is provided for users to email enquiries and ask for help from GEO’s curators.
The Affymetrix page is probably the most useful for UK plant sciences. Spreadsheet-based submission is recommended for Affymetrix deposits, so users should submit an Excel metadata worksheet, CEL files, and processed data for example a Tiling Array. The page gives advice on how to find certain information is given on finding GEO-specific information, and there are template and example spreadsheets.
Once submitted, your dataset becomes a GEO accession and can be identified with a unique accession number. The accession number should be used when you or anyone else references or links to your dataset, which seems like an easy means of tracking its usage within the community.