Law and order : a return to 'proper' policing, who are visible and accessible - with a minimum height and fitness requirement, to have a presence, and not just PSCOs who do not do a lot but look good and merely tick a 'community' box.
Zero tolerance of petty crime: littering - including cigarette butts, spitting, antisocial behaviour.
Local government: Get rid of any extra layers of expense, namely police commissioners and area mayors.
Health and Social Care: a total re-think and overhaul. Return health care to a national health service and not local trusts, etc.
Infrastructure and travel: re-nationalise railways; create nationalised reliable, convenient, accessible and affordable local transport systems.
Illegal immigration: If France can say 'they can't return to our shores once in the Channel', then we can refuse to have the illegal boats land on our shores too. Start being a sovereign nation and have the bottle to say 'no', including to the ECHR.
Legal migrants: Welcome!
Asylum seekers: These should be processed in the first safe country where they arrive - processing centres staffed by multi-national agencies, with officers appropriate to where people want to seek safety. Processing would be quickest and fast tracked for those arriving who have not thrown away identifying documents.
Any foreign national will automatically forego a 'right to family life' at the first strike - any criminal activity at all means they have disrespected their host country, so they will be repatriated on the first available plane/boat. The family will have the choice to remain without the criminal, or to join them.
Housing: so much to do - a start would be compulsory purchase of buildings standing unoccupied, including warehouses, etc. Large warehouses could be converted to flats.
So many 'what ifs' and 'yes, buts' and much fine tuning needed, but the above list would at least be a start toward mending this broken nation.