What will the main source be for your Opera? DVD/BluRay or CD? What about radio?
Your £800 is going to be spread fairly thin if it has to cover good speakers, amp, cd and tuner.
I would suggest investigating the
Marantz M-CR603 'all-in-one' (£450). 60watts per channel, FM/DAB/internet radio, CD player, optical digital connection to your TV or DVD/Bluray player.
5 stars from WHF and a favourable review in last month's issue of Gramophone magazine by our own Andrew Everard (who apparently had great fun trying it with a pair of his PMC GB1 speakers that now cost £1500 brand new!)
That would leave you £350 for speakers whereas an £800 'seperates' set-up would only leave about £200 - £250 per component depending on how many sources you need.
If you could find another £100 then you could partner the M-CR603 with something like the KEF Q300s that are - by all accounts - an ideal match.
I should qualify my suggestion by saying I only have feedback from other owners and reviewers to go on (hence a suggestion rather than a recommendation).
(Also I am buying the M-CR603 in two weeks time so have been researching people's thoughts about it.)
There is also the Arcam Solo-Mini (that can be
found in Richer Sounds for £549 now.) However that is only 25watts per channel and lacks ethernet/internet radio and lacks a digital optical input. (The best way of connecting your new TV or BluRayDVD).