Completely screwed

[Grahamm]

This is a three year old bike that has done 8000 miles- not a winter hack!

I'd look at making a claim under the Sale of Goods Act and/ or the Sale and Supply of Goods to Consumers Regulations 2002 which say (paraphrased) Goods must be of satisfactory quality and fit for purpose. If a product develops a fault after six months but within six years and it's reasonable for that product to last that long and you can demonstrate that the fault was present at time of purchase then you can require the retailer to refund you or repair or replace them (provided that the option wouldn't incur excessive cost).

Now I'd think that it's reasonable to expect that the plug isn't going to rust through and cause problems within three years (provided you've not grossly mistreated the bike!) so the fault may well have been present at time of purchase.

I'd contact your local Trading Standards/ Citizens Advice who can probably give you the full details, but I'd say there's good grounds for trying to claim.