Amazon have a few balance bikes on sale at the moment, with prices starting from £27.99. Some of these below are from private sellers, so if you click on the link you'll have to select 'other sellers' to find these prices. That also means some of them charge delivery, but the prices I've listed below are still good value.
If you've been specifically after a wooden balance bike, the Vinsani ones* are also £27.99 now, but there's a delivery fee of £4.99 on them. I do love both the Blue Flame and Pink Snowflake though.
However, if shipping puts you off - it does me - there's a lovely Plum blue and purple Cogs bike*, which is lovely and also £29.99 .