We now offer a SIPP Administrator account at Interactive Brokers UK Limited. That is, your SIPP Administrator can open a master account with us (at no cost). Afterwards, their clients (sub accounts) can trade their SIPP through us. 
Our fees: 
- $5,000 initial deposit. 
- $10 minimimum brokerage fee per month. 
- IB brokerage fees applicable e.g., $0.005 per US share (all in), GBP 6.00 per bargain, all in (=< GBP 50,000 in trade value (NOTE: Stamp duty applies). 
- Market data fees applicable. 
Benefits: 
- Trade in over 80 global exchanges. 
- Trade stocks, options, futures and etc. 
-  We support over 40 order types. 
- We offer live charts. 
- Account protection up to $30 million. 
If you want more information contact our London office 020 7 776 7801.