Party Poker is fine as a starter for online poker because it is still a HUGE site with lots of traffic. Unfortunately if you only use Maestro as a deposit option, then you will be unable to deposit at a lot of US sites (eg, Full Tilt Poker
, Bodog). Poker Stars and Ultimate Bet do accept Maestro but I personally found the players here quite tough and I know you can only withdraw by cheque at UB.
Also, many sites (Paradise and Absolute for example) only send a cheque if you cash out and this can take some time to arrive. See this link for details:
But my biggest regret was not making enquiries into rakeback deals before downloading software. Before taking the plunge, you might want to enquire into the world of "rakeback deals" as these really do give your bankroll a lift.
By the way, if you have a decent computer PKR is a 3D site that is brilliant for beginners (rake at low-limits is kinda high though).
For a good initial sign-up bonus boost, definitely go for Coral Poker or Paddy Power Poker. William Hill
also do a good £25 per month deal.
Hope this helps (sorry if I have rambled).