Its that time of the year where my broadband is up for renewal.
For my line BT Wholesale state a maximum achievable speed of 50mbs.
However any provider I go to will only offer me a maximum of 33mbs (my BT Broadband current package speed)
Why cant i find a provider that would offer what BT wholesale says the line can support?
You won't have been quoted a single figure, it will be a range, and that range is an estimate. If your actual line speed is 33Mbps, then that's what you'll get. It will be the same for all providers, since they all use the same Openreach DSLAM and copper wire.
Where did you get the 33Mbps figure? Make sure you are talking about sync speed reported by the modem, not a speedtest.net or similar; the speedtest.net result will always be lower by ~10%. The sync speed should be available from the router's web interface.