To improve your euro rate with Thomas Exchange Global (different from Thomas Exchange), you need to book online at bestforeignexchange.com. You don't actually need to enter any information except a name, then just show the booking on your phone and state your name. No ID is required for exchanges under £2000 dealt solely in cash.

The improved rate is updated on the hour from 10am to 6pm on working days, at 10am on Saturday, so depending on your schedule, you can rebook at a different branch if the actual interbank rate changes.

I have to say, I've been using them for years and they have become much less flexible than they used to be. Before you could just rock up and they'd give you the better rate. Nowadays they will make you book it while you are standing in front of the counter.

Previously if I wanted to sell 95 euros to £, I could give them a €100 and they would give me the pounds and a €5 in change. They also used to accept dirty old torn notes.... and round the GBP amount to the nearest 20p in my favour. Now, even if the GBP amount I'm due is £99.99, they will insist on counting out £4.99 in coins "for the CCTV"; they won't let me give them 1p and get two £50s.